Probably the easiest thing to do for this integration is to take the existing JCA mail adatper that allows for message inflow and enhance it to include a specific JBoss Mail listener. I would imagine, as Adrian suggested in the JIRA comments, that this would be much more efficient.
I have to familiarize myself with the JBMS API a bit, but I can probably give an estimate on time frame by the end of the week.
After that I can just knock it out and let you know when it's wrapped up.
Okay. No rush. I posted it for 2.0. (like 1 yr out)