qmail and reverse lookups

stu at spacehopper.org stu at spacehopper.org
Fri Sep 14 18:40:28 BST 2001

>How can I get qmail to give a convincing host name when connecting
>to a remote mail server? NTL don't give me a permanent internet-wide
>host (apart from pc1-reda3-0-cust222.bre.cable.ntl.com, but that could
>change since I'm on DHCP) so I dont see how user or host masquerading
>could help (without supplying a valid false hostname).
Very few servers verify the hostname matches your IP address, they just 
check it exists in DNS. (They also will not receive mail from a lot of 
windows mailers - an ISP should only validate the HELO string if they 
really like doing tech support as it can spontaneously combust and the 
fix is non-obvious :)

You don't want to use any hostname used by any system you are sending 
mail to (for example: if you set your hostname to mail.example.com and 
connect to a mailer answering with mail.example.com in the SMTP banner 
your mailer will kill the connection as it detects the loop).

I think this is control/me (I don't use qmail often so not 100% sure) - 
in Sendmail you would set class Dj or in Postfix it's myhostname= 
(although I think for those two changing hostname is enough).

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