2 questions about relay mail servers and secondary mail servers.

[Tim]

On Wed, 2007-05-02 at 11:25 -0400, Dan McCullough wrote:
> I hope everyone is having a good day or evening depending on where you
> are, if I woke you I apologize.

/me grumbles about e-mails keeping him up all night.  Damn noisy bytes
moving through the LAN cabling at all hours...

> I am looking to add redundancy and solve some ongoing mail issues.  My
> first issue is that I want to setup a second mail server to act as a
> fail over mail system, so that if the first one is unavailable there
> is a small fail-over until the other one is fixed, turned on, plugged
> in, whatever.  Now for some information I am using Fedora, Postfix,
> Dovecot, etc for the mail server setup.  Also the system does not
> store emails, except in the case that someone is out of the office,
> but as a rule very few people have mail stored on the server.
> 
> Are there steps out there to follow?

You need to learn how to set MX records in DNS.  You list several, you
assign priorities, the one with the highest gets used first, if
possible.

> Are there pro's and con's?

You should have more than one mail server, it's considered bad technique
to just use one.  It's more maintanance work for you, of course.

> The other thing that I am looking to do is for our satellite offices
> is installing small mail relay servers, that will allow internal staff
> to relay mail, rather then connecting to the vpn and sending mail that
> way.  One thing that I have noticed is that the smaller offices are on
> DSL and have some issues when sending large > 5MB attachments, which
> is a lot of their mail, and we will have issues where the mail server
> here will not get all the data in time and drop the connection before
> it has finished.  So my thinking was give them a relay mail server
> that would send mail here, if it dropped it would continue retrying
> until successful, unless I am missing the point.  However I have been
> told that mail relay might be a problem with DSL connections as those
> typically get labeled as spam since they are dynamic IP addresses,
> technically our IP addresses are labeled dynamic even though their ISP
> consider them static.

You can accept mail from where you like, on your own systems (do that
sensibly, of course).  It's up to you whether your mail systems consider
such addresses to be carrying spam.  You can pre-arrange for certain
things to be deemed okay for you.  You'd just need to make sure that
whatever sends mail *out* of your system to other systems isn't
considered one of those risky dynamic IPs.

NB:  More than it being a dynamic versus static situation, it's more a
case of ranges of IPs being used by ISP's clients, and those range of
addresses being deemed more likely to be used for spamming than well
known, more official, mail servers.

-- 
(This box runs FC5, my others run FC4 & FC6, in case that's
 important to the thread.)

Don't send private replies to my address, the mailbox is ignored.
I read messages from the public lists.