Not all AVs scan email, not all AVs scan at the same depth/degree, so it is hard to make a balanced comparison.
NOD32, KAV, BitDefender, AVG, Symantec...
Only have problems with avast since the default settings in this version was changed...
If works fine before, why change? Why not adjust to all the majors programs?
And I'm not speak only about me, but for the others users that doesn't perceive nothing of computers...
These users just want to install the AV, and don't want "complicated" settings to change...
I know some users that install the programs, if they doesn't works, just uninstall and try other...
But this is my opinion...