Dev APIs / Email API / MailerSend

MailerSend

OPERATIONAL

Since Feb 2026 · 25 incidents · status.mailersend.com · checked just now

User reportsVisitors who said it's down for them, per hour over 24 hours. Not from the status page. Never counted in grades.
…
CompareAdd to stackStatus page
GradeA+Last 90 days
A+PRODA+SHIP

Overview

30d90d1y
Admitted uptimeCustomer time not hit, by the provider's own account. Regional and partial incidents count in part.
100.000%Grade A+
IncidentsEverything posted on the status page except scheduled maintenance.
00 Sev 1
Fully downMost customers down, by the provider's own account.
0m
Median fixMedian time to resolve. Half of incidents were fixed faster.
–
LongestLongest Sev 1–2 incident, start to resolved.
–
Since lastTime since the last counted incident was resolved.
1796d 1h

By area

A+Production
0INCIDENTS
0mAFFECTED
Your users are hit: apps, APIs, databases, inference
Worst, 1y
SEV 1Feb 19, 2026 · 0mEmail activity data
SEV 2Feb 19, 2026 · 0mThe issue has been resolved
SEV 2Feb 19, 2026 · 0mWe are experiencing a technical issue
0 in the last 6 months.
A+Shipping
0INCIDENTS
0mAFFECTED
You can't deploy, build or manage: CI, CLI, dashboard, auth, billing
Worst, 1y
SEV 3Feb 19, 2026 · 0mWe are experiencing a technical issue
SEV 3Feb 19, 2026 · 0mWe are experiencing a technical issue
SEV 3Feb 19, 2026 · 0mAPP and API downtime
0 in the last 6 months.
CleanSev 3–4Sev 1–2No data

Trend, last 12 months

0 in the last 6 months.

Severity mix

Sev 1 · Lights outProd site, API or database down, or data loss0
Sev 2 · BleedingProd degraded or partly down0
Sev 3 · Can't shipCan't deploy, build or manage it0
Sev 4 · PapercutDocs, status page, slow dashboard0

When it breaks

Start times, last 12 months, UTC.

What breaks

No components named in the last 12 months.

Communication

Updates eachStatus page updates per incident, on average.
2.2Last 12 months
Update gapMedian time between status page updates during an incident.
54mLast 12 months
PostmortemsSev 1–2 incidents with a published write-up.
0 of 22Sev 1–2

Incident history

Feb 19, 20260mSEV 4
Technical issuesA technical issue in the MailerSend app may have caused problems for some users; the text names no specific function or region.AI-graded · some customers
Why this grade
  1. RULES · SEV 1
    Sev 1 from the incident title (no components listed)
  2. CLAUDE · SEV 4 · SUBSET · LOW CONFIDENCE
    A technical issue in the MailerSend app may have caused problems for some users; the text names no specific function or region.
  3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
3 updates
  1. 09:45 UTC · investigating
    We are currently investigating this issue.
  2. 12:05 UTC · resolved
    We experienced a technical issue in the MailerSend app that may have caused problems for some users. The issue has been fixed. We apologize for any inconvenience.
  3. 12:05 UTC · resolved
    We experienced a technical issue in the MailerSend app that may have caused problems for some users. The issue has been fixed. We apologize for any inconvenience.
Source
Feb 19, 2026 – Sep 4, 2024-767450mSEV 2
We're experiencing a technical issue - delays on webhooks and bulk email sending6 incidents
  1. Thu, Feb 19 15:35 UTC0mSEV 2
    We're experiencing a technical issue - delays on webhooks and bulk email sendingBulk email sending and webhook delivery were delayed for an unspecified period and scope; the provider resolved it the same day.AI-graded
    Why this grade
    1. RULES · SEV 2
      Sev 2 from the incident title (no components listed)
    2. CLAUDE · SEV 2 · UNCLEAR · MEDIUM CONFIDENCE
      Bulk email sending and webhook delivery were delayed for an unspecified period and scope; the provider resolved it the same day.
    3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
    2 updates
    1. 16:28 UTC · investigating
      We are experiencing a technical issue that might cause some delays while using the bulk email endpoint and webhooks. All of our engineers are working hard to fix the issue as soon as possible. Thank you for your understanding, The MailerSend team
    2. 16:45 UTC · resolved
      Our team successfully identified and patched the underlying problem, and the incident has been resolved. Thank you for your patience, The MailerSend team
    Source
  2. Thu, Feb 19 15:35 UTC0mSEV 2
    We are experiencing a technical issueBulk and single email sending slowed, and delivered events were delayed, for a few accounts for about two hours. Cause was a memory leak on sending servers, fixed by a restart. A more scalable sending infrastructure was planned for rollout.AI-graded · some customers
    Why this grade
    1. RULES · SEV 2
      Sev 2 from the incident title (no components listed)
    2. CLAUDE · SEV 2 · SUBSET · MEDIUM CONFIDENCE
      Bulk and single email sending slowed and delivered events lagged for a few accounts for about two hours.
    3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
    4 updates
    1. 16:00 UTC · investigating
      We are experiencing a technical issue with bulk sending that cause a delay in email sending. Our engineers are working hard to resolve the issue within the next couple of hours. We appreciate your patience.
    2. 17:31 UTC · investigating
      We are continuing to investigate the issue. The /email endpoint is also showing signs of delayed sending. Emails are queued and sent, but the delivered event is being delayed.
    3. 18:07 UTC · resolved
      The technical issue has been resolved. The email sending are back to normal. Thank you so much for your patience.
    4. 18:17 UTC · resolved
      We experienced slowdowns in sendings, on our single and bulk email endpoints. This affected a few accounts for around 2 hours. Our team investigated the issue and found that our sending servers had a memory leak. After the restart, the slowdowns were reduced, and the speed of sending went back to normal. For the past few weeks, we have been working on a more scalable sending infrastructure, and we plan to roll it out this week. This will address these problems so they do not happen again. We understand you have emails to deliver, and an apology will not mean much right now. We wanted to be transparent and let you know that we are 100% focused on fixing the issue and improving our product. Thank you for your understanding, The MailerSend team
    Source
  3. Thu, Feb 19 15:35 UTC0mSEV 2
    We're experiencing a technical issueEmail API requests were delayed for an unspecified set of users for about 30 minutes before MailerSend resolved the incident.AI-graded
    Why this grade
    1. RULES · SEV 2
      Sev 2 from the incident title (no components listed)
    2. CLAUDE · SEV 2 · UNCLEAR · MEDIUM CONFIDENCE
      Email API requests were delayed for an unspecified set of users for about 30 minutes before MailerSend resolved the incident.
    3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
    2 updates
    1. 05:34 UTC · investigating
      We are experiencing a technical issue that might cause some delays while using the app. All of our engineers are working hard to fix the issue as soon as possible. We understand that you have emails to deliver and an apology will not mean much right now. But we wanted you to know that we are 100% focused on fixing the issue and ensuring this doesn’t happen in the future. Thank you for your understanding, The MailerSend team
    2. 06:00 UTC · resolved
      This incident has been resolved.
    Source
  4. Thu, Feb 19 15:35 UTC0mSEV 2
    We're experiencing a technical issueEmail sending and delivery were delayed for an unspecified share of customers; no components were listed and the text is thin.AI-graded
    Why this grade
    1. RULES · SEV 2
      Sev 2 from the incident title (no components listed)
    2. CLAUDE · SEV 2 · UNCLEAR · LOW CONFIDENCE
      Email sending and delivery were delayed for an unspecified share of customers; no components were listed and the text is thin.
    3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
    2 updates
    1. 23:44 UTC · investigating
      We are experiencing a technical issue that might cause some delays while using the app. All of our engineers are working hard to fix the issue as soon as possible. We understand that you have emails to deliver and an apology will not mean much right now. But we wanted you to know that we are 100% focused on fixing the issue and ensuring this doesn’t happen in the future. Thank you for your understanding, The MailerSend team
    2. 00:26 UTC · resolved
      This incident has been resolved.
    Source
  5. Thu, Feb 19 15:35 UTC0mSEV 2
    We're experiencing a technical issueEmail sending and delivery were delayed by an unspecified technical issue; the text gives no scope or cause.AI-graded
    Why this grade
    1. RULES · SEV 2
      Sev 2 from the incident title (no components listed)
    2. CLAUDE · SEV 2 · UNCLEAR · LOW CONFIDENCE
      Email sending and delivery were delayed by an unspecified technical issue; the text gives no scope or cause.
    3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
    2 updates
    1. 20:31 UTC · investigating
      We are experiencing a technical issue that might cause some delays while using the app. All of our engineers are working hard to fix the issue as soon as possible. We understand that you have emails to deliver and an apology will not mean much right now. But we wanted you to know that we are 100% focused on fixing the issue and ensuring this doesn’t happen in the future. Thank you for your understanding, The MailerSend team
    2. 21:30 UTC · resolved
      This incident has been resolved.
    Source
  6. Thu, Feb 19 15:35 UTC0mSEV 2
    We are experiencing a technical issueEmail sending through the API and SMTP failed, and the whole app was inaccessible. A third-party storage provider caused the problem. It was temporarily fixed, then resolved about 32 minutes after it began.AI-graded
    Why this grade
    1. RULES · SEV 1
      Sev 1 from the incident title (no components listed)
    2. CLAUDE · SEV 2 · UNCLEAR · MEDIUM CONFIDENCE
      Email sending via API and SMTP went down, and app access was lost too; the text does not say how widely.
    3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
    4 updates
    1. 10:28 UTC · investigating
      We are experiencing a technical issue causing email sending outage with API and SMTP as well as access to the whole app. All of our engineers are working hard to fix the issue as soon as possible. We apologize for this downtime. We know that you have emails to deliver, so we're 100% focused on resolving this and preventing future issues. You can check the status page for regular updates. Thank you for your understanding, The MailerSend team
    2. 10:31 UTC · identified
      The issue has been identified and has been caused by a third-party storage service provider. We are actively working on implementing a solution and will let you know when the fix has been released.
    3. 10:37 UTC · monitoring
      The issue has been temporarily fixed and is now being monitored, we are waiting for updates from our third-party service. If you are still experiencing issues, please contact customer support via live chat or [email protected].
    4. 11:00 UTC · resolved
      The technical issue has been resolved. The App is back to normal. Thank you so much for your patience.
    Source
Feb 19, 20260mSEV 2
The issue has been resolvedStorage problems caused 500 errors on the API and SMTP, so some emails could not be sent. Errors began around 2:46 UTC and SRE found the storage fault at 4:31 UTC. Cleanup began at 4:57 UTC, followed by mitigations for storage utilisation and alerting. The provider marked it resolved and promised a fuller explanation. The update dates show 2022, not the header's 2026.AI-graded
Why this grade
  1. RULES · SEV 2
    Sev 2 from the incident title (no components listed)
  2. CLAUDE · SEV 2 · UNCLEAR · MEDIUM CONFIDENCE
    API and SMTP requests returned 500 errors, so some emails could not be sent; the text does not say how many users were hit.
  3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
2 updates
  1. 02:30 UTC · resolved
    Users were facing 500 server errors on the API and SMTP connections and as a result, were unable to send some emails. The issue has been resolved. Thank you so much for your patience. We sincerely apologize for the inconvenience. A full explanation of what happened is on the way.
  2. 07:52 UTC · resolved
    Users have faced a lot of 500 server errors from 2:46 am UTC on the morning of 10th Oct, 22. SRE has been paged at 4:31 am UTC and noticed it was a storage issue. The storage caused errors while creating new files in storage for cache or message content, etc. Our SRE team started cleaning up the storage at 4:57 am UTC and put mitigation measures in place so storage utilization would be better managed and would send alerts in case of failure.
Source
Feb 19, 20260mSEV 3
We are experiencing a technical issueThe MailerSend dashboard was unavailable for about 11 minutes; email processing continued and no emails were lost.AI-graded
Why this grade
  1. RULES · SEV 2
    Sev 2 from the incident title (no components listed)
  2. CLAUDE · SEV 3 · GLOBAL · MEDIUM CONFIDENCE
    The MailerSend dashboard was unavailable for about 11 minutes; email processing continued and no emails were lost.
  3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
2 updates
  1. 12:19 UTC · investigating
    We are experiencing a technical issue in the MailerSend app: the dashboard is unavailable. Our team is working to fix the issue as soon as possible. We will update the status page as it's resolved. None of the other pages are affected and emails are still being processed.
  2. 12:30 UTC · resolved
    The incident was resolved, no emails have been lost during the process.
Source
Feb 19, 20260mSEV 2
APP and API downtimeThe app and API were down after an unexpected outage; the text gives no scope or duration.AI-graded
Why this grade
  1. RULES · SEV 2
    Sev 2 from the incident title (no components listed)
  2. CLAUDE · SEV 2 · UNCLEAR · LOW CONFIDENCE
    The app and API were down after an unexpected outage; the text gives no scope or duration.
  3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
1 update
  1. 12:00 UTC · resolved
    We had an unexpected downtime due to a data migration. It has been resolved, apologies for any inconvenience caused.
Source
Feb 19, 20260mSEV 4
We are experiencing a technical issueA faulty latest release caused a technical issue in the MailerSend app for some users. The release was reverted and services were reported operational on November 16. Analytics data stayed delayed, and the app was reported back to normal on November 17.AI-graded · some customers
Why this grade
  1. RULES · SEV 1
    Sev 1 from the incident title (no components listed)
  2. CLAUDE · SEV 4 · SUBSET · LOW CONFIDENCE
    The MailerSend app had a technical issue for some users after a release, with latency and delayed analytics; the release was reverted.
  3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
8 updates
  1. 14:30 UTC · investigating
    We are experiencing a technical issue in the MailerSend app that may affect some users. Our team is working to fix the issue as soon as possible. We will update the status page as it's resolved.
  2. 14:31 UTC · investigating
    We detected the problem with our latest release and the team is investigating what is causing it. We will update our status page as soon as we have more information.
  3. 15:05 UTC · monitoring
    We reverted our latest release and continue monitoring any performance degradation. The activity page might have some latencies. Our team is still investigating what is causing it.
  4. 18:17 UTC · monitoring
    We are applying measures to stop any further issues.
  5. 00:12 UTC · monitoring
    Services are operational and we are monitoring the situation.
  6. 10:22 UTC · monitoring
    Analytics data is delayed at this time, our development team is working on a solution.
  7. 15:15 UTC · monitoring
    We are working on a remedy, team will provide details at a later time.
  8. 08:31 UTC · resolved
    The technical issue has been resolved. The App is back to normal. Thank you so much for your patience.
Source
Feb 19, 20260mSEV 2
Degraded performanceAPI performance was degraded, but updates never say what failed or which customers were hit.AI-graded
Why this grade
  1. RULES · SEV 2
    Sev 2 from the incident title (no components listed)
  2. CLAUDE · SEV 2 · UNCLEAR · LOW CONFIDENCE
    API performance was degraded, but updates never say what failed or which customers were hit.
  3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
2 updates
  1. 12:42 UTC · identified
    The issue has been identified and a fix is being implemented.
  2. 13:36 UTC · resolved
    This incident has been resolved.
Source
Feb 19, 20260mSEV 2
Backend server problemsOne backend database server went down; the text does not say which customer requests failed or for how long.AI-graded · some customers
Why this grade
  1. RULES · SEV 2
    Sev 2 from the incident title (no components listed)
  2. CLAUDE · SEV 2 · SUBSET · LOW CONFIDENCE
    One backend database server went down; the text does not say which customer requests failed or for how long.
  3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
1 update
  1. 11:00 UTC · resolved
    We had a downtime on one of our backend database servers. The problem has been fixed.
Source
Feb 19, 2026 – Dec 3, 2024-637944mSEV 1
Email activity data3 incidents
  1. Thu, Feb 19 15:35 UTC0mSEV 2
    We are experiencing a technical issueLatency issue caused delays for some but not all users of the API; resolved within about two hours.AI-graded · some customers
    Why this grade
    1. RULES · SEV 2
      Sev 2 from the incident title (no components listed)
    2. CLAUDE · SEV 2 · SUBSET · MEDIUM CONFIDENCE
      Latency issue caused delays for some but not all users of the API; resolved within about two hours.
    3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
    2 updates
    1. 13:29 UTC · investigating
      We are experiencing a latency issue that may cause delays for some but not all users. Our engineers are working hard to resolve the issue. We are grateful for your patience.
    2. 15:11 UTC · resolved
      This incident has been resolved.
    Source
  2. Thu, Feb 19 15:35 UTC0mSEV 2
    We are experiencing a technical issueA rate-limiting issue caused emails sent to Gmail addresses to be deferred, delaying delivery. Engineers implemented a fix, and the provider reported deliverability back to normal about 2.5 hours after the first update.AI-graded · regional
    Why this grade
    1. RULES · SEV 2
      Sev 2 from the incident title (no components listed)
    2. CLAUDE · SEV 2 · REGIONAL · MEDIUM CONFIDENCE
      Emails to Gmail addresses were deferred by a rate-limiting issue, delaying delivery; other mailbox providers were not reported affected.
    3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
    3 updates
    1. 12:34 UTC · investigating
      We are aware of an issue that is currently affecting our email delivery to GMail accounts. Due to a rate-limiting issue, emails sent to GMail addresses are being deferred, resulting in delays in delivery. Our engineers are actively investigating the cause of this rate-limiting issue and are working diligently to resolve it as quickly as possible. We understand the frustration and inconvenience this may cause, and we deeply apologize for any disruptions this issue may have created for you or your business.
    2. 13:34 UTC · monitoring
      A fix has been implemented, new emails should not be deferred.
    3. 14:06 UTC · resolved
      Deliverability rate should be back to normal.
    Source
  3. Thu, Feb 19 15:35 UTC0mSEV 1
    Email activity dataAll existing email activity data was lost, and the text does not say how many customers were hit. Counted as Sev 1 for data loss or exposure.AI-graded
    Why this grade
    1. RULES · SEV 1
      Sev 1 because the provider reported data loss or exposure
    2. CLAUDE · SEV 1 · UNCLEAR · MEDIUM CONFIDENCE · DATA LOSS
      All existing email activity data was lost, and the text does not say how many customers were hit.
    3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
    1 update
    1. 13:00 UTC · resolved
      We are sorry to inform you that all existing email activity data has been lost. All new data is in place, and email activity functionality works now. Please do contact our support if you need assistance.
    Source
Feb 19, 20260mSEV 2
We experienced a technical issueA release caused an outage on MailerSend's sending servers, and emails sent through the SMTP relay were lost. SMTP was reported operational at 12:45 UTC and the incident was resolved at 16:52 UTC. The text gives no customer count.AI-graded
Why this grade
  1. RULES · SEV 1
    Sev 1 from the incident title (no components listed)
  2. CLAUDE · SEV 2 · UNCLEAR · MEDIUM CONFIDENCE
    SMTP relay sending servers went down after a release, and emails sent through the relay were lost; the reach across customers is not stated.
  3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
3 updates
  1. 10:30 UTC · monitoring
    We experienced a technical issue during our release, which caused an outage on our sending servers. Our engineers worked on a fix as soon as we identified the root cause. This incident happened at 10:36 am UTC+2 and resulted in losing emails sent with our SMTP relay. We apologize for this downtime. We know you have emails to deliver, so we have been 100% focused on resolving this and preventing future issues. You can check the status page for regular updates. We appreciate your understanding, The MailerSend team
  2. 12:45 UTC · monitoring
    SMTP is now operational.
  3. 16:52 UTC · resolved
    This incident has been resolved.
Source
Feb 19, 20260mSEV 2
Technical issue on our SMTP proxySome users could not connect to the SMTP proxy for about 40 minutes due to a certificate problem causing TLS errors.AI-graded · some customers
Why this grade
  1. RULES · SEV 2
    Sev 2 from the incident title (no components listed)
  2. CLAUDE · SEV 2 · SUBSET · MEDIUM CONFIDENCE
    Some users could not connect to the SMTP proxy for about 40 minutes due to a certificate problem causing TLS errors.
  3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
1 update
  1. 14:30 UTC · resolved
    Some of our users experienced a service interruption today between 4:30 and 5:10pm (GMT+2) when connecting to our SMTP proxy. After investigation, we found out the certificate on our SMTP proxy caused some clients problems when connecting, resulting in TLS-related exceptions being reported. The issue has now been resolved. We sincerely apologize for the inconvenience. Thank you for your understanding, The MailerSend team
Source
Feb 19, 20260mSEV 2
We're experiencing a technical issue resulting in a 401 error increaseMailerSend's API began returning 401 authentication errors to some callers while sending email. Engineers worked on a fix, and the provider later reported the incident solved, with no more 401 errors on API calls. No cause was given.AI-graded
Why this grade
  1. RULES · SEV 2
    Sev 2 from the incident title (no components listed)
  2. CLAUDE · SEV 2 · UNCLEAR · MEDIUM CONFIDENCE
    API calls returned 401 errors for an unspecified share of requests; the provider says the issue is resolved.
  3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
2 updates
  1. 08:30 UTC · investigating
    We are experiencing a technical issue that might result in 401 errors while using the API. All of our engineers are working hard to fix the issue as soon as possible. We understand that you have emails to deliver and an apology will not mean much right now. But we wanted you to know that we are 100% focused on fixing the issue and ensuring this doesn’t happen in the future. Thank you for your understanding, The MailerSend team
  2. 09:30 UTC · resolved
    The incident was solved. You should no longer receive 401 errors when calling the API.
Source
Feb 19, 20260mSEV 2
Delayed delivery timeEmail delivery was delayed by unexpectedly high sending load; emails were still being sent and the slowdown was later absorbed.AI-graded
Why this grade
  1. RULES · SEV 2
    Sev 2 from the incident title (no components listed)
  2. CLAUDE · SEV 2 · UNCLEAR · MEDIUM CONFIDENCE
    Email delivery was delayed by unexpectedly high sending load; emails were still being sent and the slowdown was later absorbed.
  3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
3 updates
  1. 10:43 UTC · identified
    Due to an unexpectedly high sending load, we're experiencing some delays in email delivery. Emails are still being sent. This should return to normal in a few minutes.
  2. 10:49 UTC · identified
    We are continuing to work on a fix for this issue.
  3. 11:28 UTC · resolved
    The slowdown was absorbed.
Source
Feb 19, 20260mSEV 2
We've experience a technical issue on our bulk endpointA faulty release broke the bulk-sending endpoint on April 10, 2024 from 12:50 to 15:12 UTC; it was rolled back. Unusual load then slowed bulk sending. A hotfix with stricter retries shipped April 11, and the bulk feature was down again 11:24 to 12:16 UTC. Total slowdown about 3h14m.AI-graded · some customers
Why this grade
  1. RULES · SEV 2
    Sev 2 from the incident title (no components listed)
  2. CLAUDE · SEV 2 · SUBSET · MEDIUM CONFIDENCE
    Bulk email sending was down or slowed for about 3 hours across two windows; other sending was not described as affected.
  3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
1 update
  1. 00:30 UTC · resolved
    We experienced a technical issue that caused delays while using the bulk endpoint. The bulk-sending feature was down between 12:50 UTC and 15:12 UTC on April 10th and between 11:24 UTC and 12:16 UTC on April 11th. We released a new version of the app at 12:50 UTC, and then, 20 minutes after the release, we identified an error and started working on a fix. At 15:12 UTC, we decided to revert to the last stable version. Around 15:58 UTC, the slowdown in the bulk sending was identified, and we started investigating. We had an unusual high load, which was slowing down the sending. At 11:24 the next day, we released a hotfix to handle this larger load by implementing a stricter retry mechanism. This amounts to 3h14 of slowdown. We understand that you have emails to deliver and an apology will not mean much right now. But we wanted you to know that we are 100% focused on fixing all issues and ensuring this doesn’t happen in the future. Thank you for your understanding, The MailerSend team
Source
Feb 19, 20260mSEV 2
Email delivery and activity status problemsBetween 08:00 and 12:00 UTC, some users experienced delayed email sending, and the activity reporting system may have shown inaccurate status. Multiple fixes were deployed. The update gives no root cause and does not say when service was confirmed normal.AI-graded · some customers
Why this grade
  1. RULES · SEV 3
    Sev 3 from the incident title (no components listed)
  2. CLAUDE · SEV 2 · SUBSET · LOW CONFIDENCE
    Some users saw delayed email sending and inaccurate activity reports for about four hours on 23 April; no outage was described.
  3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
1 update
  1. 08:00 UTC · resolved
    Today, we encountered technical challenges that led to delays in email delivery and discrepancies in activity reporting. Specifically, between 08:00 UTC and 12:00 UTC, some users may have experienced delays in sending emails, and our activity reporting system may have provided inaccurate information. Upon identifying these issues, our team immediately sprung into action and we deployed multiple solutions to fix said problems. We understand the frustration and inconvenience that delayed email delivery and inaccurately reported activity statuses can cause, especially when you rely on our platform for important communications. We want to sincerely apologize for the recent disruptions you may have experienced. An apology may not mean much, but please know that our entire team is committed to preventing similar incidents in the future.
Source
Feb 19, 20260mSEV 2
Mail transfer agent delivery report delayBetween May 18 05:15 UTC and May 19 16:05 UTC, some users saw delayed email activity reporting and wrong timestamps on delivered statuses. The cause was a mail transfer agent delivery report delay. Email delivery was not impacted.AI-graded · some customers
Why this grade
  1. RULES · SEV 2
    Sev 2 from the incident title (no components listed)
  2. CLAUDE · SEV 2 · SUBSET · MEDIUM CONFIDENCE
    Email activity reports and delivered-status timestamps were delayed or inaccurate for some users; email delivery itself was not affected.
  3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
1 update
  1. 14:00 UTC · resolved
    We have recently encountered technical difficulties that have affected the accuracy of email activity reporting within our platform. Between May 18 05:15 UTC to May 19 16:05 UTC, some users may have experienced delayed email activity reporting and inaccuracies in the timestamp on delivered activity statuses. Upon thorough investigation, we have determined that these issues stemmed from our mail transfer agent delivery report delay (email delivery was not impacted). This unforeseen challenge resulted in disruptions to our usual service standards, for which we sincerely apologize. We understand the importance of timely and accurate email communication for your operations, and we recognize the impact that these issues may have had on your experience. Please know that addressing these challenges is our top priority, and we believe that we have diligently worked towards resolving this. Your trust in our service means everything to us, and we are committed to earning back your confidence by delivering the dependable performance you expect and deserve. Should you have any questions or concerns, please do not hesitate to reach out to our support team. We are here to assist you in any way we can.
Source
Feb 19, 20260mSEV 2
We are experiencing a technical issueEmails to Gmail recipients were deferred and delayed for an unspecified period; other mailbox providers were not mentioned as affected.AI-graded · regional
Why this grade
  1. RULES · SEV 2
    Sev 2 from the incident title (no components listed)
  2. CLAUDE · SEV 2 · REGIONAL · MEDIUM CONFIDENCE
    Emails to Gmail recipients were deferred and delayed for an unspecified period; other mailbox providers were not mentioned as affected.
  3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
2 updates
  1. 18:00 UTC · investigating
    We are experiencing a technical issue with the deferrals for emails sent to Gmail domains that may prevent some users from delivering emails to certain Gmail recipients. The emails will be delivered normally once the issue is fixed. Our engineers are working hard to resolve the issue within the next couple of hours (rough estimate). We are grateful for your patience.
  2. 11:20 UTC · resolved
    The problem should be resolved now, sorry for the inconvenience.
Source
Feb 19, 20260mSEV 2
Delays in webhook deliveries on 2-DEC-2024Webhook deliveries to customer apps were delayed for about 5.5 hours; the text does not say how many customers were hit.AI-graded
Why this grade
  1. RULES · SEV 2
    Sev 2 from the incident title (no components listed)
  2. CLAUDE · SEV 2 · UNCLEAR · MEDIUM CONFIDENCE · BACK AFTER -640145M
    Webhook deliveries to customer apps were delayed for about 5.5 hours; the text does not say how many customers were hit.
  3. Claude Haiku 5.5 · prompt v11 · Oct 24, 2026 · Raw record
1 update
  1. 02:30 UTC · resolved
    We want to acknowledge and apologize for an issue that caused delays in webhook deliveries. The issue began at approximately 2024-12-02 16:30 UTC and was resolved at 2024-12-02 22:00 UTC. The system is now fully operational.
Source

Peers, 90 days

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