[SATLUG] Setting up email server

[Brad Knowles]

On 9/10/07, Samuel Leon wrote:

>  I have another question.  What is everyone using for client access?  Pop3
>  or IMAP?

I use both.  In theory, the advantage with IMAP is that you leave 
your mail on the server, and you only sync your client(s) to the 
server.  That way, you can see and access all your mail from various 
different clients.  Of course, that puts all your eggs in that one 
server basket, and if that one server dies then you lose all your 
mail.  In essence, this is the AOL model of mail, with all the 
problems that entails.

In my case, I actually download all my mail to my local machine using 
POP3 for one account and IMAP for another.  The IMAP service is from 
a back-up account I have with a different provider, and which is 
pretty much completely unpublished.  I have aliases configured at 
certain places to send copies of important incoming mail to both my 
primary and secondary accounts, but I only respond to messages from 
the primary.

>  I am only familiar with pop3.  Are there any advantages to IMAP besides
>  security?

With IMAP and the right server and the right client, you can set up 
filtering rules on the server side which will automatically put 
messages into appropriate sub-folders, before you ever log on.  The 
client can further apply intelligence to the connection, and only 
download those parts of messages that you've told it you always want 
to see.  That way, you could always leave all copies of large files 
(videos, pictures, etc...) on the server, and only download them to 
your client when you actually want to view them.

IMAP also assumes that you will have multiple simultaneous processes 
accessing your mailbox, so you should see new mail coming in pretty 
much as it comes in, and you can be accessing the same mailbox from 
multiple clients simultaneously (maybe you get up from your desktop 
where you leave your mail client running, and you can still access 
all your mail from another system somewhere else).


POP3 can't really do any of these things.

OTOH, IMAP is a guaranteed way to build up huge massive mailboxes 
that may take a long time to load and search, and the bigger the 
mailbox the bigger the risk that something will come along and wipe 
everything out.

When you build an IMAP server, you need to build it more robustly 
than you would a POP3 server, since it has to remain online with much 
greater reliability and availability, and it has to be able to 
survive a much more punishing environment.

With a POP3 server, if it goes down, then the only thing you should 
have lost would be whatever mail was on the box since the last time 
you logged in and downloaded all your mail.


You can encrypt both POP3 and IMAP connections, and IMAP has a wide 
variety of authentication methods that are available.  Unfortunately 
due to the "lowest common denominator" problem, both protocols end up 
being installed and used in most places in the least secure manner 
possible.

>             Also is it necessary to have a DNS server along with the
>  email server?  All the help pages that I am following seem to have a DNS
>  setup section alongside the email server setup section...

It's not strictly required, no.  However, it can be extremely useful 
and increase both your reliability and your performance.  I do 
generally recommend setting up at least a caching/recursive-only 
nameserver on each and every mail server that you install.

-- 
Brad Knowles <brad at shub-internet.org>
LinkedIn Profile: <http://tinyurl.com/y8kpxu>