Thunderbird and Avast Compatability Issue

Have been away from Thunderbird and windows for sometime, but have continued to use avast in various windows environments
At present cannot send or receive emails with Avast active Mail Shield.

Operating System

Windows 8 64-bit
CPU Intel Core i3 3110M @ 2.40GHz 44 °C Ivy Bridge 22nm Technology
RAM 12.0GB Dual-Channel DDR3 @ 798MHz (11-11-11-28)
Motherboard LENOVO Lenovo G580 (CPU Socket - U3E1) 45 °C
Graphics Generic PnP Monitor (1366x768@60Hz) Intel HD Graphics 4000 (Lenovo)
Hard Drives 932GB Seagate ST1000LM024 HN-M101MBB (SATA) 44 °C
Optical Drives Optiarc DVD RW AD-7740H
Antivirus avast! Antivirus antivirus Enabled
Company Name AVAST Software Product Version 8.0.1489.0
Virus Signature Database Up to date
Windows Defender Antivirus Disabled Virus Signature Database Up to date
Java Java Runtime Environment Path C:\Program Files\Java\jre7\bin\java.exe
Version 7.0 Update 25 Build 17

http://www.avast.com/faq.php?article=AVKB91