[NTLUG:Discuss] Sendmail question

[Stephen Klein]

"Gregory A. Edwards" wrote:
> 
> In trying to get sendmail to masquerade my public domain from an internal
> host I've got all my local domain names being rewritten but why do some
> ISPs still reject with the following message:
> 
>    ----- Transcript of session follows -----
> ... while talking to smtp4.jps.net.:
> >>> MAIL From:<greg at eagle.newage.local> SIZE=381
> <<< 501 <greg at eagle.newage.local>... Sender domain must exist
> 
> Greg E
> 
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> http://ntlug.org/mailman/listinfo/discuss


It's an anti-spam block that some ISP's use.  Most SPAMer's use fake
domains to get around some spam filters that block based on the domain
name.  Basically, the recieving mail server does a DNS lookup and
rejects the e-mail message if the lookup fails.  Cyberramp (My former
ISP, dang IA!) did this because they were having trouble with SPAM
clogging their mail servers.


Stephen Klein