I'm having real problem with sending mail to domains where the namesevers are NOT on the server and so no mail users or MX record is set for that domain.
The error messages are either
Recipient address rejected: User unknown in virtual alias table
relay=none, delay=0.11, delays=0.11/0/0/0, dsn=5.4.6, status=bounced (mail for mydomain.co.uk loops back to myself)
If I set up the DNS record on the server for that domain to include the real NS and MX records then I can send mail from my mail client (as user who is on the server).
However trying to send mail via the domains website contact form fails
postfix/smtp: B2DFEC9C05F1: email@example.com, relay=mx0.123-reg.co.uk[18.104.22.168]:25, delay=40, delays=0.12/0/20/20, dsn=5.0.0, status=bounced (host mx0.123-reg.co.uk[22.214.171.124] said: 550-Verification failed for firstname.lastname@example.org 550-Unrouteable address 550 ATLAS(2503): Sender verification failed (in reply to MAIL FROM command))
This is on CentOS 6.7 using Postfix 2.6.6
I have another server where I do not have use the real NS for the domain or set up MX records and it works fine. This is on Centos5.11, Postfix 2.3.3
I have cross checked the postfix main.cf and even used the same settings apart from the server name in the mail destination but it still fails.
I'm running out of ideas as to where else to look in order to make the new server work the same way as the current one.
Thanks in advance.