sendmail 550 Host unknown

[Dave Anderson]

OK, this is a weird one. A customer tried to send an email and my machine
kicked it back with a 501 Sender domain must exist. So I added his domain
to /etc/mail/access and rebuilt the sendmail.cf. OK he can send me email
now. But I cannot send to him I get 550 Host unknown. Now I can send via
Outlook but when I try with sendmail on my UX box 550. Any ideas?

Dave

[Andrzej Filip]

Post by Dave Anderson
OK, this is a weird one. A customer tried to send an email and my machine
kicked it back with a 501 Sender domain must exist. So I added his domain
to /etc/mail/access and rebuilt the sendmail.cf. OK he can send me email
now. But I cannot send to him I get 550 Host unknown. Now I can send via
Outlook but when I try with sendmail on my UX box 550. Any ideas?

Send them a message with DNS tracking turned on.

sendmail 8.12 - as root run:
echo ("subject: test"; echo ) | sendmail -Am -d8.20 -oi -v ***@customer.com

older sendmail version:
echo ("subject: test"; echo ) | sendmail -d8.20 -oi -v ***@customer.com