[ale] Backup MX basics

[agcarver+ale at acarver.net (Alex Carver)]

On 4/21/2014 15:13, JD wrote:
> On 04/21/2014 05:48 PM, Alex Carver wrote:
>> I'm was pondering a backup MX for my server (I still haven't fixed its
>> clicky IDE drive) but it occured to me that I don't actually know how a
>> backup is configured to A) be the backup and B) make sure that it
>> delivers/synchronizes mail to the primary eventually.
>>
>> Searching around online hasn't quite given me the basics, it just gives
>> me configuration parameters for different daemons without a full
>> explanation.  For example, I would assume that a backup has a more
>> liberal delivery timeout (e.g. ten days instead of four) but nothing
>> I've found makes any of that clear.
>>
>> Suggestions for things to look at or just personal experiences?
> 
> 
> There is a number in the MX DNS record. Primary is lower than 2ndary. That's it.
> 
> The synchronization is up to you. I don't bother.  If you make the primary and
> secondary only tiny "front-end" servers (mainly spam/AV filtering), then have a
> backend-email server to handle all the approved access by end-users (IMAPS (993)
> / authenticated SMTPS (465) only and for outbound email, then you don't have to
> worry about synchronization. If the back-end server is unavailable, mail gets
> held at the front-end(s).  If one front-end goes down, the other receives mail
> still and forwards to the back-end. These front-ends can be tiny - 256MB/2G of
> storage.  Simple, easy and the backend server can be located almost anywhere
> (perhaps you don't want all email static on VPS storage).
> 
> My backups of front-end email servers ignores the actual email - just handles
> the list of packages installed and the settings.  120 days of backups is ...
> 27MB total.
> 
> Clearly the back-end email server backups are much, much larger.

I don't need to get that complicated.  It's my private server.
Occasionally it (or its connection) goes down so I just wanted a backup
to queue mail to be delivered later when it comes back up.  No real need
for a front/back-end setup.  I don't even store my mail on it for very
long, it all gets downloaded later via Thunderbird.  The whole server
right now is using an 8GB drive.