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.