>> No, mail spools/queues do not need replication. Stuff in the queue are >> usually deleted in a second and such dynamic change is not worth >> replicating. If you do put the queue on a distributed filesystem, in >> most cases you cannot have more than one instance running save for >> sendmail. >> > > outbound mail can sit in queues retrying for hours negotiating their way > into the greylists of the likes of Yahoo. I guess if you don't mind > the possibility of messages getting lost around a server failure event, > then its no big deal, for sure. > That only leaves putting the queue on a distributed filesystem. Replication will not be a complete solution to that and qmail queues cannot be replicated. Then there is the question of whether to leave a message in the queue for more than 4 hours given the expectation of email to be more or less instantaneous.