Can I add resiliance by adding multiple smtproutes values?

I would like to be able to place multiple entries into /var/qmail/control/smtproutes in order to add resilience. Much like having multiple MX records I would like to beable to have multiple entries for each domain listed sothat should the first host be down, qmail will attempt to deliver to the second host.

Can this be done??

Answer:

Simply put, no.

Unfortunately, the smtproutes function doesn't work that way. It honors only the first instance of an artificial route, thus

bobsgarage.gov:mx42.xo.mil

bobsgarage.gov:mx12.elsewhere.mil

Will always go to mx42.xo.mil. mx12.elsewhere.mil will never be reached.

The best you can do - and it's not very good - is to create a round-robin dns entry. while qmail will continue to try to deliver to the down server, the repeated deferrals will eventually 'hit' the other server.during my experiments with roundrobin dns, I found that if one of the two hosts that i wanted to process messages in parallel went (or was taken) offline, deliveries continued as normal, they simply all gradually 'migrated' over to the server that was up. From tinydns data:

+pmx.smileglobal.com::4

+pmx.smileglobal.com::4

from smtproutes:

:pmx.smileglobal.com