[CentOS] Re: Mail server setup for small ISP

Fri Jan 4 15:30:47 UTC 2008
Ugo Bellavance <ugob at lubik.ca>

Christopher Chan wrote:
> Fajar Priyanto wrote:
>> On Friday 04 January 2008 10:30:32 Ugo Bellavance wrote:
>>>> AFAIK, redundancy for mail server seldom uses linux-ha/any other 
>>>> failover
>>>> stuffs. It is most common to use 'backup MX' in DNS settings. So, when
>>>> the main server in unreachable, the sender mail server would try to the
>>>> secondary MX through DNS query.
>>> That's the easy part, but where do you store the e-mail once you have
>>> accepted it?  If the pop/IMAP server is down for a while, people won't
>>> be able to retreive their e-mail...
>>
>> The secondary MX will temporarily store the mails. And when the 
>> primary server is up again, it will get all the mail from the 
>> secondary. Yes. there will be a down time in terms of mail service for 
>> users.
>>
>> Maybe others can recommend a better best practice for this.
> 
> Yes. No backup mx. You ought to have a cluster of mail servers to accept 
> mails for your domain if you need HA. Otherwise, let incoming emails 
> queue at their sending hosts as setting up a 'backup' mx that will only 
> hold the email and then pass them onto the 'primary' is really pointless 
> and only serves to 1) delay delivery of mail and 2) delay notification 
> of mail delay to the sending party. It is no longer acceptable today to 
> wait for a week before notifying the sender of non-delivery. The idea of 
> a backup mx no longer fits today's communications.


I agree, and I don't want to have any client not being able to contact 
the pop/IMAP server for more than 15 minutes.

Ugo