I put out the release announcement for M4 pre2 here: http://jboss.org/jbossBlog/blog/acoliver/?permalink=JBoss_Mail_Server_M4_pre2_released.txt.
BTW, I switched my mail server to M4-pre2 and also to postgresql (after running nicely on mysql for a while). ATM for some reason MySQL was faster. I suspected this had more to do with valid connection checking using "ping" than anything else, but even after removing it the MySQL + paged store is faster. I wonder if Postgresql + paged store would be faster than MySQL or if once you've worked around the blob issue with paged store, MySQL is just FASTER. Potentially this may also have to do with the block size in the large object API...but I dunno.
All in all Postgresql is still faster in M4-pre2 than MySQL was in M3. I find myself illmotivated to switch back to mysql knowing how badly they implement blobs but may try paged store on postgresql which should theoretically work anyhow. I'm also going to grab the MySQL connector/j for 5.0 and see if its fixed yet in 5.0...
I could really use some help testing this release on Oracle as the box I was doing my Oracle testing on is toast. So if you have the cycles and the oracle, give me a hand please!
Many comparisions in the past that I have seen where mysql was faster than postgres was apples agains pears. Postgres was running fully in transaction mode, while mysql in I-dont-care-mode.
Just as a side note. This doesn't apply to you(r setup) anyway