It is about Mozilla Thunderbird 17.0.2 ESR, operating on Win XP SP3. In the add-ons window (list of all installed plug-ins) it presents ESET Smart Security Extension 6.0.308.0. It claims this plug-in was incompatible, therefore disabled. The EAV 6.x solution present on system is set to Email Client Protection enabled and integrated into Thunderbird, and scanning mail messages while the send and read access. Cleaning in no cases is set. Where does this incompatibility come from? The issue could already be observed with EAV 5.x, perhaps also with 4.x.