[SOLVED] sendmail stopped working user unknown

mfoley · 03-24-2021, 04:17 PM

I've been using sendmail for a very long time, but every so often I get stumped. I have a server at 24.96.253.243 running sendmail 8.15.2. The sendmail.cf file has not be touched for 4 years, yet for some months now this host is unable to send outgoing emails. I just tried:

Code:

echo testing | mail -r mfoley@novatec-inc.com -s testing mfoley@novatec-inc.com

novatec-inc.com is a personal computer also running sendmail. I've spoofed the reply address to try and eliminate 24.96.253.243 host/domain issues. On novatec-inc.com nothing at all appears in the maillog. On host 24.96.253.243 I get:

Code:

Mar 24 16:58:32 bu6500 sm-mta[16714]: 12OKwWmP016714: <mfoley@novatec-inc.com>... User unknown
Mar 24 16:58:32 bu6500 sendmail[16713]: 12OKwVdv016713: to=mfoley@novatec-inc.com, ctladdr=mfoley@novatec-inc.com (1002/301), delay=00:00:01, xdelay=00:00:00, mailer=relay, pri=30322, relay=[127.0.0.1] [127.0.0.1], dsn=5.1.1, stat=User unknown
Mar 24 16:58:32 bu6500 sm-mta[16714]: 12OKwWmP016714: from=<mfoley@novatec-inc.com>, size=322, class=0, nrcpts=0, proto=ESMTP, daemon=MTA, relay=localhost [127.0.0.1]

Host 24.96.253.243 is connected to the Internet and can see other hosts, including novatec-inc.com via 'ping', 'host' and 'ssh'.

That IP has FDQN bu6500@ohprs.org. The only thing that has changed in the past 6 months is the MX record for the hprs.org domain is now at mail.protection.outlook.com. What could be the problem? Is one of the server's attempting to verify the user with Exchange? Other things I can check?

floppy_stuttgart · 03-26-2021, 02:26 AM

Hello,
I tried to send from a raspberry pi4 mails from a yahoo account few months ago. it did not work (whatever.. setup.. security..).
Now I am using a googlemail account for sending mails out (in case of videomotion). the mails are sent and arrive at.. the yahoo account.
this is not a precise guess for you: but probably security setup from your mail server.
then proposal (workaround..): setup a googlemail account ;-)

mfoley · 04-06-2021, 10:29 AM

I "solved" the problem by designating a SMART_HOST (relay) on the ohprs.org domain. That worked. I still don't know why it did not work standalone. There's probably a logical explanation, but I don't have the patience to research it!