Which version of Java should be used with JBMS 1.0M4 and later

versions: 1.0M4, 1.0M5-pre1

JBoss Mail Server 1.0M4 releases require JDK 5.0 (aka 1.5).  We recommend the latest available JDK 5 VM from either Sun or BEA (JRockit).  Generally speaking JRockit usually benchmarks faster than Sun's VM for most applications, preliminary testing gives Sun JDK 5 the advantage with JBMS.

Most platforms now support JDK 5.0 from Windows to Linux to AIX to Mac OS X and even mainframe/midrange platforms.