Sendmail reject trumps whitelist?

Kevin Miller Kevin_Miller at
Thu Nov 16 17:28:11 GMT 2006

Brett Charbeneau wrote:
> Greetings all,
>  	I've set up sendmail to reject incoming messages with a 554
error if
> they are listed in by sticking this line in my
> file: 
> FEATURE(`dnsbl',`',`"554 Rejected " $&{client_addr} > "
> BLACKLISTED found in"')dnl
>  	Now this list tends to get mad a AOL and Hotmail mail servers
> obvious reasons and therefore ALL mail from these domains, legit or
> not, gets rejected.
>  	I'm trying to figure out if a sender's address is specifically
> whitelisted in MS *AND* their server is on if the
> sender will get rejected or allowed for delivery.
>  	I'm betting the Sendmail reject comes first in the process, but
> asking those in the know to be sure...

Sendmail comes first.  The process is sendmail is contacted by external
servers.  It accepts or rejects the message based on how it's configured
and stores it in /var/spool/ (if accepted).  MS then runs its
test on it, where it's accepted or rejected, and moves it to
/var/spool/mqueue where it's again picked up by sendmail and sent to the
appropriate internal server/user.

Highly recommend the MailScanner book for a good understanding of the
process.  Understanding the flow of the mail is important to tweaking
your system.  Since spammers are constantly changing their tactics, mail
admins also have to...

Kevin Miller                Registered Linux User No: 307357
CBJ MIS Dept.               Network Systems Admin., Mail Admin.
155 South Seward Street     ph: (907) 586-0242
Juneau, Alaska 99801        fax: (907 586-4500

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