Found the server log for when the emails started to fail. Normally there would be (5) emails per weekday, one for each inc backup completed and then (3) emails on each full backup weekend day (the 6th client only does full backup on weekend). As the log shows, it started failing some of the emails for a few days before failing on all attempts.
Wednesday: got 3 emails, 2 fails.
2017-10-11 18:29:49: WARNING: Sending mail failed. Failure when receiving data from the peer(ec=56),
2017-10-11 19:59:52: WARNING: Sending mail failed. Failure when receiving data from the peer(ec=56),
Thursday: received all 5 emails.
No email failures.
Friday: got 4 emails, 1 fail.
2017-10-13 20:11:14: WARNING: Sending mail failed. Failed sending data to the peer(ec=55), RCPT failed: 550
Saturday: no emails
2017-10-14 08:09:30: WARNING: Sending mail failed. Failed sending data to the peer(ec=55), RCPT failed: 550
2017-10-14 11:19:08: WARNING: Sending mail failed. Failed sending data to the peer(ec=55), RCPT failed: 550
2017-10-14 20:20:47: WARNING: Sending mail failed. Failed sending data to the peer(ec=55), RCPT failed: 550
Sunday: no emails
2017-10-15 04:50:16: WARNING: Sending mail failed. Failed sending data to the peer(ec=55), RCPT failed: 550
2017-10-15 10:23:24: WARNING: Sending mail failed. Failed sending data to the peer(ec=55), RCPT failed: 550
2017-10-15 14:45:27: WARNING: Sending mail failed. Failed sending data to the peer(ec=55), RCPT failed: 550
Monday: no emails
2017-10-16 17:03:36: WARNING: Sending mail failed. Failed sending data to the peer(ec=55), RCPT failed: 550
2017-10-16 17:12:50: WARNING: Sending mail failed. Failed sending data to the peer(ec=55), RCPT failed: 550
2017-10-16 17:31:30: WARNING: Sending mail failed. Failed sending data to the peer(ec=55), RCPT failed: 550
2017-10-16 18:10:01: WARNING: Sending mail failed. Failed sending data to the peer(ec=55), RCPT failed: 550
2017-10-16 19:56:05: WARNING: Sending mail failed. Failed sending data to the peer(ec=55), RCPT failed: 550
Tuesday: no emails
2017-10-17 17:04:26: WARNING: Sending mail failed. Failed sending data to the peer(ec=55), RCPT failed: 555
2017-10-17 17:26:13: WARNING: Sending mail failed. Failed sending data to the peer(ec=55), RCPT failed: 555
2017-10-17 17:36:46: WARNING: Sending mail failed. Failed sending data to the peer(ec=55), RCPT failed: 555
2017-10-17 18:14:36: WARNING: Sending mail failed. Failed sending data to the peer(ec=55), RCPT failed: 550
2017-10-17 19:57:55: WARNING: Sending mail failed. Failed sending data to the peer(ec=55), RCPT failed: 550
The log from then on repeats with all failures for each day, until…
2017-10-29 07:33:48: WARNING: Sending mail failed. Failed sending data to the peer(ec=55), RCPT failed: 555
2017-10-29 10:11:43: WARNING: Sending mail failed. Failed sending data to the peer(ec=55), RCPT failed: 555
2017-10-29 15:08:25: WARNING: Sending mail failed. Failed sending data to the peer(ec=55), RCPT failed: 555
The “failed” code changed to “555” for some reason. No configuration changes were made to UrBackup during this time.
Any ideas where to look next? Thanks.