please take a look at
Bug 30538 – VersaMail 3.5.4 does not sync mails
This issue is different from 30304 as 30304 affects all phones. 30538 however only affects Treos. The logs we received early on only showed the symptoms of 30304. As a result 30304 masked the issue of 30538 until we received new logs that showed a different issue.
This fix is in 5.0.9.