Server
The tail of mail.log — Postfix, OpenDKIM and the milters. For one message, open it from a log page instead.
Sep 21 14:01:52 postfix/smtp[2131]: 4XcB9q0Lw2z1: to=<m.keller@gmx.de>, relay=mx00.gmx.net[212.227.15.9]:25, delay=0.8, status=sent (250 Requested mail action okay) Sep 21 14:01:52 postfix/qmgr[58]: 4XcB9q0Lw2z1: removed Sep 21 14:00:18 postfix/smtpd[2129]: connect from mail.uni.example[192.0.2.77] Sep 21 14:00:18 postfix/smtp[2130]: 4XcB8z5Tn1z1: to=<dev@lists.example.org>, relay=mx.internal[10.0.4.2]:25, status=sent (250 2.0.0 Ok: queued) Sep 21 13:58:09 postfix/smtp[2123]: 4XcB7k2Jm9z1: to=<noc@example.org>, relay=mx1.example.org[192.0.2.10]:25, status=deferred (451 4.7.1 Greylisted, try again in 5 minutes) Sep 21 13:57:41 postfix/smtpd[2119]: NOQUEUE: reject: RCPT from bulk.example[198.51.100.90]: 550 5.1.1 <sales@lists.example.org>: Recipient address rejected: unknown recipient Sep 21 13:44:02 postfix/smtp[2101]: 4XcB2m7Hd4z1: to=<jobs@acme.io>, relay=none, status=deferred (connect to 10.0.4.12[10.0.4.12]:2525: Connection timed out) Sep 21 13:41:19 postfix/smtp[2098]: 4XcB1c3Rk8z1: to=<j.doe@nonexistent.example>, status=bounced (Host or domain name not found) Sep 21 13:40:02 journal-milter[40]: rate limit: app=prod-server 201/200 in 3600s — tempfail at MAIL FROM Sep 21 13:00:00 opendkim[39]: key table reloaded (3 domains)