Yeah, that was it. Funny thing is I wasn't in Avast preferences for quite some time and have no idea how it could have been enabled.

Now, the problem is this: I've got "mail support" unchecked but Mail app. is launched along with Avast when I login or restart . When I check Avast's preferences "mail support" is checked, even though I haven't touched it. I understand that this is a known issue and will be corrected in the next Avast for Mac release.
I have already removed the GetRuleScript.txt" file but it still reappears in Avast's contents/resources folder.

OK, the file reappeared once after deleting it, so far, but not a second time, yet.