conflict with comodo antispam

??? I was using comodo antispam before installing comodo antivirus. Surprisingly, though enabled , antispam does not work anymore.
I had uninstalled the antivirus to test another free av and comodo antispam started working.
Subsequently i have reinstalled comodo av and again I find antispam is not working.
Is it necessary to uninstall antispam and reinstall it again ?

Its not necessary but it seems somthing went wrong there. Try uninstalling both. Then Install Comodo AntiSPam and check it is working properly. Now you install CAV and let us see.