Heysender experienced a minor incident on September 4, 2026, lasting —. The incident has been resolved; the full update timeline is below.
Update timeline
- resolved Sep 04, 2026, 12:00 PM UTC
Type: Incident Duration: 1 hour and 20 minutes Affected Components: Outgoing SMTP Sep 4, 12:00:30 GMT+0 - Monitoring - Since 9:50 CEST this morning Microsoft has had issues receiving email. This means that many emails sent to Office365 recipients will result in a soft bounce with this message: 52.101.68.10 failed after I sent the message./Remote host said: 451 4.7.500 Server busy. Please try again later from \[REDACTED\]. (S77714) \[[DB1PEPF000509E3.eurprd03.prod.outlook.com](http://DB1PEPF000509E3.eurprd03.prod.outlook.com) 2026-09-04T08:16:36.825Z 08DF04AEA47F75BA\]/ If you have access to the Office365 admin page they have created an issue to follow here: We're monitoring the issue but for now there is nothing we can do to force emails through. Emails sent during Microsoft downtime will be tried again for the following 48 hours until delivery is possible. (We're mainly creating this issue to have a place to point clients to for updates. There is nothing we can do inhouse to solve the issue.) Sep 4, 13:20:08 GMT+0 - Resolved - This incident has been resolved by Microsoft. We're working on emptying the queues and we expect all email to be delivered soon.