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Re: postfix or exim?



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On Saturday 12 Apr 2003 11:29 am, Burkhard Ritter wrote:
> Hello.
>
> I want to set up an internet server (static ip) which should handle some
> mail. It would accept the appropriate mails and users could get them with
> pop or imap. The volume would be rather small.
>
> I had a look at several articles and also searched the mail archieves.
> Apparently postfix is the preferred solution, but I didn't really get the
> reasons for this. Lately I used exim locally and was quite happy with
> this.
>
> What are the advantages of postfix? What are your recommendations?
>
> Thanks in advance.
>

I did look at both a while ago - but I have been running exim happily for a 
year.  Let me give a the two differences that I have noticed  and are my 
impression are the main changes.  I may be entirely wrong so don't take my 
word on it.

Message throughput

With exim all messages go into a single message queue, and if they get stuck 
for any reason (can't send out because you have a dialup connection for 
instance) you frequently need to scan the whole queue.  This can lower the 
overall throughput if you have a large volume of messages to process. (I 
don't think this is the case if no queue forms) Postfix I never quite 
understood, but got the impression that this was not the case and so probably 
was slightly faster on throughput

Flexibility with mail manipulation

I orginially stopped using Postfix because I found a problem with configuring 
it.  I think I was trying to specify an address (mine) that all mail that 
didn't have a match elsewhere was sent to.  I could only do that if I was 
delivering locally, but I wanted to deliver to cyrus and I couldn't combine 
the two.

On the otherhand, Exim has the concept of directors and routers which takes a 
while to get your head around, but once you do, see immensly flexible.  Each 
one allows you to make a special checks of the mail, and if it meets the 
criteria in the director (or router) you can take special action by passing 
it to a transport your name to process it further.  Each transport then can 
do its own address manipulation and then deliver it further.

This allows you (for instance - as I have) to configure exim to manage mailman 
mailing lists without having to know exactly how many mailing lists there 
are.  Making it trivial to add new ones.

I also do a number of other manipulations that I think would be quite 
difficult in postfix
- - spam check mail through an external program and back into exim again (I can 
check the header fields to see if the check has happened)
- - allow special prefixes to addresses to bypass the spam checker
- - allow special suffix to local addresses to force them to be sent out into 
the internet (via my isp) 
etc
- - I pass all messages through a filter and drive my logging from it.

It has always seemed to me (but bear in mind I know understand Exim quite 
well, but don't understand Postfix as much) that Postfix's manipulation, was 
sufficiently flexible for most cases, but only just so, where as Exim had 
flexibility in reserve, and when I needed to do something strange, I have 
always found I could.


Hope that helps

- -- 
Alan Chandler
alan@chandlerfamily.org.uk
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