Mail cannot be sent using office365 Outlook: 451 4.7.1 Service unavailable - try again later

Created:

2016-12-18 06:52:02 UTC

Modified:

2017-08-08 13:35:35 UTC

0

Was this article helpful?


Have more questions?

Submit a request

Mail cannot be sent using office365 Outlook: 451 4.7.1 Service unavailable - try again later

Applicable to:

  • Plesk 12.5 for Linux

Symptoms

Mails are rejected by server if they are sent using Office365 Outlook solution. The following error in maillog :

    Dec  1 12:48:20 server.hostname postfix/smtpd[7304]: CF1092521FC: milter-reject: DATA from mail-eopbgr20072.outbound.protection.outlook.com[10.20.30.40]: 451 4.7.1 Service unavailable - try again later; from=<user1@example1.com> to=<user2@example2.com> proto=ESMTP helo=<EUR02-VE1-obe.outbound.protection.outlook.com>

Cause

There is a probability that receiving messages from Exchange Online Protection IP addresses is not allowed.

Resolution

Have more questions? Submit a request
Please sign in to leave a comment.