Duration: 1 hour and 20 minutes

Affected Components: Outgoing SMTP

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..

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: <https://admin.cloud.microsoft/?source=applauncher#/servicehealth/:/alerts/EX1467029> 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.).

Duration: 26 minutes

Affected Components: Incoming SMTP, API

Sep 1, 09:11:10 GMT+0
Completed - Maintenance has completed successfully..

Sep 1, 08:45:01 GMT+0
Identified - Maintenance is now in progress.

Aug 31, 12:23:13 GMT+0
Identified - We will be running the maintenance between 10:45 am and 11:15 am tomorrow..

Aug 28, 13:15:43 GMT+0
Identified - We are planning for a scheduled maintenance on the 1st of September during working hours. The specific time will be added to this case when we have it. During the maintenance you might experience delays in connecting to our SMTP and API service but the delay should be no longer than a few seconds. .

Duration: 4 hours and 42 minutes

Affected Components: Outgoing SMTP, API

Aug 10, 14:55:12 GMT+0
Resolved - Due to an issue with our hosting provider Heysender could not send email for a few hours this afternoon. The issue has been solved and we're monitoring the state of the service for the rest of the day..

Aug 10, 10:13:00 GMT+0
Investigating - We're currently experiencing issues sending e-mails from our system. We're investigating the cause..

Duration: 3 hours and 18 minutes

Affected Components: App

Apr 16, 20:19:00 GMT+0
Resolved - This incident has been resolved..

Apr 16, 18:19:19 GMT+0
Monitoring - Outgoing traffic sent while the issue persisted will have been delayed but started being sent when we implemented the fix..

Apr 16, 18:00:09 GMT+0
Monitoring - We implemented a fix and are currently monitoring the result. The root cause is once again our Object Storage solution which broke. We have switched over to our secondary provider. This means that preview of emails sent before this update will not work as well as the resend functionality. We expect to solve these issues over the next couple of days but for now we are monitoring to ensure everything works as intended..

Apr 16, 17:53:18 GMT+0
Identified - We have identified the root of the issue and are mitigating it now..

Apr 16, 17:00:32 GMT+0
Investigating - We are currently investigating an issue resulting in events not being registered correctly. Emails are leaving the servers but the response is not saved correctly. We'll update when we know more. .

Duration: 11 minutes

Affected Components: Incoming SMTP, Outgoing SMTP, App, API

Dec 11, 12:05:39 GMT+0
Resolved - We're back online and all systems are operational. Many apologies for the issues - we're working closely with our service provider to avoid similar incidents going forward..

Dec 11, 11:54:20 GMT+0
Investigating - All systems are down. We are currently investigating this incident..

Duration: 9 hours and 46 minutes

Affected Components: Incoming SMTP, Outgoing SMTP, API, App

Dec 4, 13:11:11 GMT+0
Postmortem - The issue was caused by a firewall issue at our hosting provider. It was solved with 10 minutes of total downtime to the system. .

Dec 4, 13:09:17 GMT+0
Resolved - This incident has been resolved..

Dec 4, 06:11:19 GMT+0
Resolved - All systems seem to be online again. We're keeping an eye on things but from here it seems to be a network issue at our hosting supplier resulting in about 10 minutes of downtime. We will update when we know more..

Dec 4, 06:05:04 GMT+0
Investigating - The issue also affects the app, API and outgoing SMTP. We're still investigating..

Dec 4, 06:01:33 GMT+0
Investigating - We're currently investigating what seems to be an issue connecting to smtp.heysender.com. New status within 30 minutes..

Duration: 51 minutes

Affected Components: App

Oct 7, 10:20:00 GMT+0
Resolved - This incident has been resolved..

Oct 7, 09:29:00 GMT+0
Investigating - We're changing our S3 provider due to ongoing issues with the current solution. This has some consequences for our clients. We will be moving to our secondary hosting provider, Leaseweb Amsterdam, who already hosts the server sending out emails. This means that it will not impact any existing or future Data Protection Agreements. Since we store copies of HTML and text content as well as attachments in S3 the move means that this data can not be accessed until we have moved all historic data from our old provider to Leaseweb. This will take some time - we do not know how long yet since our current provider is having performance issues. Thus, we have disabled the resend function in Heysender which makes it possible to resend an email to a recipient. Since we can not access the content of the email we can not resend it. We apologise for any inconveniene caused. Get in touch with support if you have any questions..

Duration: 21 hours and 6 minutes

Affected Components: API, App

Oct 3, 09:20:00 GMT+0
Resolved - All services are back to normal. We are in touch with our provider about how to solve this issue for good..

Oct 2, 12:40:00 GMT+0
Monitoring - We're sending emails again but we're not storing HTML and text content or attachments. We'll update when this changes..

Oct 2, 12:14:00 GMT+0
Identified - Once again our hosting provider has issues with S3 hosting. We are making changes in order to handle the issue but mail queues should be up and running again soon. New update in 20 minutes..

Duration: 2 days, 13 hours and 37 minutes

Affected Components: API, Incoming SMTP, App, Outgoing SMTP

Sep 29, 08:30:00 GMT+0
Resolved - All systems are running as expected. We're marking this as fixed..

Sep 27, 16:11:00 GMT+0
Monitoring - We're sending emails without issues but we're still not logging HTML and text content or attachments. We have decided to let everything stabilise so on Monday we will bring everything back to working order..

Sep 27, 08:10:00 GMT+0
Monitoring - Our hosting provider is still working on bringing their S3 storage back up. We're sending emails without issues but we're still not logging all data due to S3 storage being offline. We will update here when we're actively logging everything again..

Sep 26, 20:45:00 GMT+0
Monitoring - We're sending emails again. We have bypassed S3 storage which we use to save HTML content, text content and attachments of sent emails. For now these will not be saved to log and will not be available for lookup in the interface. As soon as S3 storage runs again we will re-enable it. We apologise sincerely for the issues this has caused. If you have any questions do not hestitate to contact support..

Sep 26, 19:30:00 GMT+0
Identified - S3 has been bypassed. We're running final tests before opening the system externally. We will update again within the next 20 minutes..

Sep 26, 19:10:00 GMT+0
Identified - We're working on bypassing S3 storage to get all systems running again. We will update again within the next 20 minutes..

Sep 26, 18:53:00 GMT+0
Investigating - Due to an issue with our hosting provider's S3 storage we're currently experiencing difficulties accepting incoming SMTP and API connections. We're looking into solutions. New status will follow in 20 minutes..

Duration: 2 hours

Affected Components: API, Incoming SMTP, App, Outgoing SMTP

Jan 15, 21:45:00 GMT+0
Completed - Maintenance has completed successfully..

Jan 15, 19:45:00 GMT+0
Identified - We will be updating a central piece of SMTP software in Heysender. This will result in a downtime on the incoming SMTP service lasting a few minutes where the SMTP service will not respond to connection requests. Afterwards, the incoming SMTP service will be running but all outgoing e-mail will be caught and saved for later delivery while we update the software. The date and time of the update is: **Tuesday 21st of January 2025 from 20:45 CET to 22:45 CET** We expect the entire process to take 1-2 hours from start to end. For the first few minutes no incoming SMTP requests will succeed and afterwards there will be a delay of up to 2 hours on outgoing e-mail. If you have any questions regarding the update please do not hesitate to get in touch with support..

Duration: 12 minutes

Affected Components: API, Incoming SMTP, App, Outgoing SMTP

Jan 7, 14:03:00 GMT+0
Resolved - This incident has been resolved..

Jan 7, 13:51:00 GMT+0
Monitoring - We are currently experiencing e-mails with logging in Heysender. Our hosting partner is updating a key part of their infrastructure which we use to store log files making us unable to handle the logs. We have made a change to the system so we bypass logging of text and HTML versions which solves the issue for now. We will update when all is back to normal..

Duration: 15 days, 21 hours and 25 minutes

Dec 19, 12:28:00 GMT+0
Resolved - This incident has been resolved..

Dec 19, 12:03:00 GMT+0
Monitoring - Due to a change in the service some webhooks changed format. This has resulted in issues with integrations parsing the webhooks. The change has been rolled back and we're working on fixing the format before we retry the webhooks with the right format. If your service responds with 200 OK when a webhook is received we will not retry the webhook. Get in touch with support if you need assistance receiving the webhooks again..