Re: Sendmail vs. Postfix vs. ?

[Travis Owens <openbook@linuxmds.com>]

Ken,

Just a little background on the two SMTP servers. These two servers are
only for delivery of mail around the Internet from server to server, and
on the server to the user's mailbox or mail directory. As far as the
user retrieving their mail, that requires a different server (IMAP or
POP)

Sendmail has been around for a long time and is the default on many UNIX
based OSes. The problem with it, is that it's very confusing to
manipulate its setup and configuration by hand. As Lee pointed out,
there are administration modules out there for easier configuration, but
if you needed to manipulate it on a machine without those helpers
installed, it can be very frustrating. Also, it's a very large program
with lots of code. This means that it's kind of bulky in processing
things and can be slow. One other very important point is the way
Sendmail has run on the system. It's permissions have been violated many
times over and caused many opening for hackers.

Postfix on the other hand is a small group of smaller programs. Due to
this group design, there are different permissions that each piece
operates, thus, only one piece of it has the permissions available to
run as root. This piece is the local delivery agent, since it must write
to all the user's mailboxes or mail directories. The important thing
about this, is that the connection to the outside world, never runs with
these permissions, meaning that it's a very secure oriented program.
Also, because the whole Postfix system is a small set of tools, it's
extremely fast. This really isn't noticeable for a small amount of
users, but when you compare it to Sendmail on a large ISP's scale,
Postfix will smoke it like it's using a walker. ;)

For the user retrieval method, I would recommend the Courier apps, which
will provide your IMAP and POP3 solutions. Also, Courier developers
liked the Dan Bernstein mail storage method called "Maildir/" (notice
the importance of the trailing slash) This method puts all the email
messages you receive into separate files which means that if one were to
be received corrupted, it will not affect any of the other messages. A
bit of history here will explain that the Sendmail method was to
concatenate all messages into one huge file and when the email client
program would connect, it would be able to separate out the emails, one
from another. The only problem with this was when you received, say 5
emails, and the 2nd one was corrupt. This threw your client off when
trying to separate the other messages and caused the connection to hang
and eventually die. There were only two options for the ISPs to do, one
was to edit the file and remove the corrupted message from the group, or
remove the whole file. As harsh as that sounds, the latter was the most
typical practice the ISPs would choose to do. So, this other method is
obviously better. Fortunately, Postfix supports this type of delivery
method. (hint, hint)

I hope this helps you!
Travis


On Fri, 2004-09-03 at 02:05, Ken Keefe wrote:
> I am going to begin working on an email server for a group ranging from
> 50 to 500 people. I have not previously worked with any kind of mail
> server and I wanted to get your opinions on which server to use. My
> understanding is that sendmail is pretty much the standard, but Mandrake
> seems to prefer Postfix. Then again, for all I know, they could be the
> same thing! 
> 
> Anyway, what mail server should I look into and why? I'd like to
> eventually be able to offer IMAP for the few that want it, but mostly I
> need POP services.
> 
> M$ servers need not apply...
> 
> Thanks,
> Ken
> 
> 
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-- 
Travis Owens <openbook@linuxmds.com>


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