MX fallback solution

[Kermit]

mangelot Wrote:I think you are suggesting to download the accounts from the secondary server?
But I was thinking of an solution on the same single ispCP server.
example:

mx10 my home ipadres
mx20 my ispcp server

when my home ip is down, the secondary mx20 will fallback the emails for the period of time mx10 is offline,
there are further no email accounts in ispCP, only the possibility of to relay/backup mail for a domain during fallback.

are I'm I talking stupid right now
I'm not so into fallback systems..
sorry for my english...

No, you're right. Or at least what you're asking for makes sense.
This kind of architecture consists in a MX host and a so-called "Backup MX", a host that queues mail for more than 72 hours until the main host is up again.
This is quickly achieved by setting two DNS records with different priority and configuring secondary SMTP as a backup MX for all domains on it. Just a matter of writing the right conf.

@ stefan> A real fallback solution should consist in a pair of (or more) identical mailservers with a failover policy, but that's hard to achieve unless you don't put mailboxes on a common storage device (such a third host) and use the two SMTP hosts to relay mails and to check mailboxes on the third one via POP3/IMAP services. Still I really don't know how POP3/IMAP servers on the market could manage concurrent access to a shared filesystem.
Anycase the trouble with this kind of topic is how to make users access their mailboxes if the primary server is down: the only solution that solves that is (as far as I know) a single storage server for MTA's virtual users tables and mailboxes. Anycase, nobody assures you that the storage server lasts forever, so you have to have a redundancy/replication solution with load balancing... things get hard on this. Off course, they get hard until you don't have enough money to spend... in theory you could consider yourself safe with three servers: 2 MXs and 1 load balancer.
Good luck!