Hello All,

My postfix server is behind nat (10.100.100.6 <> 202.1.2.3)
my ip masquerade is 202.7.8.9

mydomain.com PTR address is 202.7.8.9
and mail.mydomain.com PTR address is 202.7.8.9

why I am unable to send email to a domain (ie. otherdomain.com)
with the following bounced back message:

This is the mail system at host mail.mydomain.com

I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can delete your own text from the attached returned message.

The mail system

<someone@otherdomain.com>: host mail.otherdomain.com[101.a.b.c] said: 450 4.7.1 Client
host rejected: cannot find your hostname, [202.1.2.3] (in reply to RCPT
TO command)

please help..

thanks a lot in advance

Regards
Win

Likely because it found your 202.1.2.3 as your mail server and did NOT find a PTR back to a name for that IP. A lot of sites these days reject mail coming from IPs that have no PTR records. Some even reject if they consider the reverse as "generic" which is the default for many reverse lookups. You need to put in a PTR that is specific to the purpose of this IP.
Is 202.1.2.3 what you have in your MX record?
Do you have a PTR for 202.1.2.3?

202.1.2.3 had PTR but this problem already solved .. by configuring my mikrotik


chain=srcnat action=src-nat to-addresses=202.1.2.3
src-address-list=10.100.100.6
out-interface=[WAN Interface]

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