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i wanna to setup postfix mail server instead of ms exchange server . we have around 8000 users , and we want to use active directory for users . how many servers do we need ? what kind of strategy we should choose ? how to use ad users in mail server ?

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@ansari definitively postfix. i find it rock solid - it's only MTA that i'm using on the production setups. but i just point out that you need more than just MTA. for pop3/imap - i've got only experience with courier and i'm happy with it, but i have not heard any complains on dovecot neither. and yes - zimbra is much more 'end-to-end' replacement for exchange, but for heavy load - i would much more trust simple postfix+courier. –  pQd Dec 25 '09 at 18:14
    
what do you think of qmail ? is it good ? in comparison with postfix –  Ansari Dec 25 '09 at 18:29
    
@ansari - i think qmail reached perfection [ that is - is not developed anymore; but it's almos same with postfix ]. i belive with qmail/exim/postfix - you can reach pretty much same result [ high stability, high performance ]; it all boils down to one question: with which of them do you feel most comfortable. –  pQd Dec 25 '09 at 18:34

4 Answers 4

up vote 5 down vote accepted

it more depends on how many messages/sec will you have to handle rather than number of users. 8k users is not a lot and you can handle such load for typical home users without problems on any modern hardware.

remember that postfix is MTA - will handle nicely mail routing / sending, but it does not provide access to the local mail store - you'll need something like courier or dovecot for pop3/imap access.

so if you look for exchange replacement - it'll have two layers [ which can run on one machine.. ]:

  1. mail routing - postfix: messages come here from the content filters; at this level decision is taken to which server mail should be delivered.
  2. mail storage - postfix + courier or similar: messages get delivered here, end-users connect to those servers to check their inboxes.

and possibly 3rd group of machine for outgoing mails

at this scale you probably want to make all the levels redundant. at the beginnign you can start with running all of those on two virtualization servers with reasonably fast io subsystem and reasonable amounts of memory [ it all depends on usage pattern - but i would start with 32GB per box, 8x 15krpm disks ].

such approach should give you quite nice scalability if you might have more users in the future.

i suggest you do not let postfix query ldap continuously to check if given mail address is valid or not. instead - use batch job that will extract all valid mail address from active directory every few hours and populates local sql database that postfix will query.

this script can give you idea how to extract addreses from ad.

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tnx , instead of postfix , what mail server do you offer me ? –  Ansari Dec 25 '09 at 18:06

I am very happy with Atmail Server at the moment. And according to their website they can handle that many users easily (My environment is smaller so I can't tell you if they really scale that well.)

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tnx . can answer this question too ? serverfault.com/questions/97347/… –  Ansari Dec 26 '09 at 8:26

Postfix with fedora directory server easy install and config/manage http://studyhat.blogspot.com/2009/10/how-to-setup-fedora-directory-server.html

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Let me ask you this - why are you using MS Exchange?

If you doing more than just email with Exchange, postfix is not likely a good solution. You need to find a mail solution that is comparable to Exchange - something like "Zimbra":

http://www.zimbra.com/

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tnx , the most important things for me are stability and trust –  Ansari Dec 25 '09 at 18:03
    
More importantly if stability and trust why aren't you using exchange? –  Jim B Dec 25 '09 at 18:33
    
we used exchange , but with a powerful server we didn't get ours goals –  Ansari Dec 25 '09 at 18:39
    
Exchange isn't just an email server - it is also a collaborative service where people can share calendars, contacts, and tasks. If your users utilize any of these features, they will not be happy when they get migrated over to Postfix and lose them. That is why I suggested Zimbra - its a postfix solution with calendaring + other Exchange-like features. That said, what is your email infrastructure like? A postfix front-end to Exchange may be more appropriate, as it will allow you to load virus-scanning/spam detecting for inbound/outbound msg and reduce load on the Exchange server itself. –  Rilindo Dec 25 '09 at 19:37
    
yes , tell me how many servers (and their properties)we need to have a optimized exchange server ? and also can you answer this question too ? serverfault.com/questions/97347/… –  Ansari Dec 25 '09 at 19:58

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