SMTP traffic loadbalancing originating from one IP - possible packet loss?

FWIW I usually don't bother with LB'ing SMTP... As you stated above, it's perfectly capable of LB'ing all by itself using MX records (i.e. multiple MX records with the same priority round robin). As SMTP isn't an interactive protocol the delay in opening a connection if the first server is down isn't usually a problem.

 

 

If you do LB it, then it's the same mechanism for recover if the server crashses between messages as if no LB was involved. Messages that have been accepted and acknowledged are gone. Messages that haven't (i.e. the one you're sending when the connection goes down) get resent. You get the same resend or duplication of message as you'd get if a non-LB'ed SMTP server crashed at exactly the same time.

 

 

H