On 06/23/2021 09:59 PM, Frank Cox wrote: > On Wed, 23 Jun 2021 21:54:02 -0400 > H wrote: > >> Can anyone suggest how to track down the app so I can reconfigure the mail >> address? > And the relevant line(s) in /var/log/maillog are.... > Here is an example line: Jun 25 03:25:40 centos7 postfix/smtp[59252]: 6AB952C03793A: to=<root at aaa.bbb.ccc>, relay=smtp.1and1.com[74.208.5.2]:587, delay=1.4, delays=0/0.02/1.2/0.23, dsn=5.0.0, status=bounced (host smtp.1and1.com[74.208.5.2] said: 550-Requested action not taken: mailbox unavailable 550 invalid DNS MX or A/AAAA resource record (in reply to RCPT TO command)) aaa.bbb.ccc above is a filler for the incorrect address, in fact a malformed address on the server itself that I need to track down, and, as I understand it, the reason smtp.1and1.com kicks it away.