Mendix Cloud EU (Frankfurt) issue sending email using SMTP relay

Update timeline

1. identified Feb 06, 2026, 03:13 PM UTC

   We have identified an issue in the region Mendix Cloud EU (Frankfurt). Customers sending email, using an SMTP relay over port 25, might be unable to deliver those e-mails. This issue is caused by one or more of our outgoing IP addresses being blocklisted by an external email security provider. We are in communication with the external email security provider to have the affected IP addresses removed from their list. Until then, our advice is to switch to a different SMTP relay provider and avoid using port 25 for sending email altogether.

2. identified Feb 11, 2026, 12:15 PM UTC

   We are continuing to work on a solution for this issue.

3. resolved Feb 24, 2026, 01:53 PM UTC

   This incident has been resolved. The affected outgoing IP addresses have been removed from the external email security provider's blocklist. Email delivery via SMTP relay from Mendix Cloud EU (Frankfurt) is operating normally again. As a general best practice, we recommend using port 587 (TLS) instead of port 25 for outgoing email. Please refer to our Sending Email documentation for recommended SMTP configuration: https://docs.mendix.com/developerportal/deploy/sending-email/#external-email-providers