Mailgun incident

Email Delivery Failures to Microsoft 365 Domains

Notice Resolved View vendor source →

Mailgun experienced a notice incident on August 17, 2026 affecting Outbound Delivery, lasting —. The incident has been resolved; the full update timeline is below.

Started
Aug 17, 2026, 08:18 PM UTC
Resolved
Aug 17, 2026, 08:18 PM UTC
Duration
—
Detected by Pingoru
Aug 17, 2026, 08:18 PM UTC

Affected components

Outbound Delivery

Update timeline

  1. resolved Aug 17, 2026, 08:18 PM UTC

    We have received confirmation that an external issue impacting email delivery to Microsoft 365 domains has been resolved. Impacted messages would have received an error stating "5.7.511 Access denied, banned sender" between Friday, August 14th and Monday, August 17th. Any failed messages will need to be resent. Information on retrying messages can be found in our Help Center here: https://help.mailgun.com/hc/en-us/articles/18596982041883-Resending-messages