Reject mail from invalid domains

[Jason Ede]

Surely it makes sense to at least check if the sender is a fully qualified domain and also that there is an MX record for that domain?

Jason



From: Koopmann, Jan-Peter
Sent: Tue 29/05/2007 08:58
To: MailScanner discussion
Subject: RE: Reject mail from invalid domains


On Tuesday, May 29, 2007 9:13 AM Jorge Costinha wrote:

> invalid domain, are domains that cannot be resolved by DNS. i belive
> it is a good practice to reduce spam and workload of mailscanner and
> spamassassin if mails coming from invalid domains are block. am i
> right?   

In theory: Yes. The question is how do you make sure the domain can be resolved? Nameservers exist? Whois is successful (would not work probably)? Sender callout (google for SAV or Sender address verification to find out that many people seriously dislike it). And even if the domain resolves you could check if the domain has valid MX records. Or SPF and so on. 

Implementation depends on your MTA of course.


Kind regards

Jan-Peter Koopmann
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