MS gateway checking for valid users before delivery

Drew Marshall drew at THEMARSHALLS.CO.UK
Thu Dec 29 13:36:36 GMT 2005

On 29 Dec 2005, at 05:21, Glenn Steen wrote:

> On 29/12/05, Pete Russell <pete at> wrote:
>> If you want a perl script that will
>> 1. query AD for ALL valid usernames
>> 2. Build the map file in the correct postfix format
>> 3. Postmap it and reload postfix
>> All you need to do is cron it and you have implemnted milter ahead  
>> for
>> postfix and exchange, let me know and i will email it to you.
>> We have been using this for years and it works flawlessly and can be
>> implmented in realtime without causing downtime.
>> Maybe its in the wiki too?
> Yes.... Didn't you write that Pete? Anyway, here's a link:
> id=documentation:configuration:mta:postfix:how_to:reject_non_existent_ 
> users#rejecting_unknown_non-local_users

Pete wrote the original for Notes/ Dominio in the old MAQ and I  
converted it to the wiki (And added a couple of bits for Exchange).  
Anyway to the OP the wiki covers how I would do it.

However, if you want to implement a milter ahead style feature,  
Postfix comes with this built in have a look at  
reject_unverified_recipient under smtpd_recipient_restrictions. You  
can read more here 
5.html#smtpd_recipient_restrictions be aware though you must have  
implemented smtp filtering on the Exchange server for this to work  
(So unknown recipients are rejected at smtp stage and not bounced  
later) or else non of these types of checks will work (No matter  
which MTA you use).


In line with our policy, this message has 
been scanned for viruses and dangerous 
content by MailScanner, and is believed to be clean.

------------------------ MailScanner list ------------------------
To unsubscribe, email jiscmail at with the words:
'leave mailscanner' in the body of the email.
Before posting, read the Wiki ( and
the archives (

Support MailScanner development - buy the book off the website!

More information about the MailScanner mailing list