James Davis wrote: > Matthew Newton wrote: > > >>Set up two hosts, on two IP addresses, with the same MX number? >> >>Seems the most obvious to me. We have three mail hubs like this; >>occasionally SpamAssassin will fail on one, but the others keep >>processing just fine. That's the nice thing about SMTP; it's >>resilient by design ;-) > > > At the moment I'm running an IMAP server directly on the MX hosts, > failing that over between the two. I want to make sure that the mail > ends up on the host with the active IMAP server - hence the rerouting to > the shared IP address. I'm thinking perhaps it would just be easier to > run the IMAP server elsewhere :-) > > James > > >
You've hit the right nail on that one. - because of retry, and/or multiple mx, a failed MTA doesn't have to be fixed in 'seconds', though minutes rather than days is nice. - but a POP or IMAP that doesn't respond to 60-second, 5-minutes, etc, checks for mail has users reaching for the phone. - likewise the 'submission' side of an MX, Unlike a 'peer' MX, it is a rare luser's MUA that can 'fall back' to a secondary MSA for sending. Once again - a failure to (be able to) send gives rise to calls for help in minutes, not hours. IMAP (including most Webmail) is particularly demanding of storage congruency - else more calls 'where has my ... folder/contents gone?' calls. No 'one size fits all' solution, but RAID, external, and 'hardware' shared, not nfs, then 'standby' MTA / MSA and POP/IMAP with an external IP-takeover 'watchdog' might at least keep it to a two-box or three-box solution. Keeping luser's mailstore in sync is IMNSHO, the biggest challenge. Bill -- ## List details at http://www.exim.org/mailman/listinfo/exim-users ## Exim details at http://www.exim.org/ ## Please use the Wiki with this list - http://www.exim.org/eximwiki/
