Previously I had a problem with Mozilla SeaMonkey mail on Win7x64.
As detailed in this forum last post February 08, 2013, 07:45:58 PM, here:-
http://forum.avast.com/index.php?topic=111925.msg892885#msg892885
I had then moved to Avira antivirus and have now uninstalled Avira to try the newest Avast 8 RC2.
I can now report that the SeaMonkey mail problem is not evident with this newer Avast version and all appears well.
I still do not know what Avast 7.0.1474 did that prevented any email client from working and no one answered my original post with any info either.
All I know is that the problem with Avast 7 was only with that version and not with the rival Avira and not with the latest Avast 8 RC2.
Hope this helps someone else.
Regards,
BobxT