I just noticed that the upload for 1.1.19.p4 failed in some way, and the wrong version is on the web server. 1.1.19.p4 has a build number starting 172.. Please check the build number by selecting About from the menu on the mailbox list screen.
The correct build numbers are
4.2 api – 17214
4.3 api – 17213
4.6 api – 17212
This has given me the opportunity to slip in an improvement to session error handling, hopefully fixing a problem that causes send/receive to stop responding under certain circumstances.