Why are my outbound messages being bounced?

Issue: My outbound messages are being bounced

Symptoms: I'm receiving an unusual number of NDRs.

Resolution: The recipient domain is unreachable.

Outbound Services may not be able to connect to the recipient domain because the attempt to look up the domain's MX records failed, or because none of the servers listed in the domain's MX records was reachable. Under these circumstances, you receive the following bounce message:

  • 451 Cannot connect to domain:domain - psmtp

Outbound Services continues its attempts to send the message for up to six hours. After six hours, the message is removed from the outbound queue, and one of two errors is returned:

  • 550 MX records inaccessible for too long for domain:domain - psmtp
  • 550 MTA inaccessible for too long for domain:domain - psmtp

Outbound Services aggregates information from all senders. Consequently, you may or may not experience the six-hour deferral window described above before the messages are bounced. If other Outbound Services customers have been attempting to send to the same unreachable domain, those attempts are tracked, and Outbound Services begins bouncing the messages six hours after the first unsuccessful message was sent, regardless of the originating customer.

Editions: This article is intended for administrators using Google Message Security and Google Message Discovery. If you're using another edition, your service may include different features from those described in this article.

Keywords: outbound, bounced