I can see that in PLESK 10.4.4 the following failure was reintroduced.
http://forum.parallels.com/showthread.php?t=108628
I also copied the mail-log entries
Mar 26 12:34:42 postfix/qmgr[29156]: CC63111D22F4: from=<
[email protected]>, size=668, nrcpt=1 (queue active)
Mar 26 12:34:42...