That's an email scrubber.
They all fart about with permissions because They want to have low permissions in case they get compromised(hacked). Sendmail and Bind run as root, which is a bad idea really. If you hack them, you have root. So all secure mail thingys change from one powerless user to another and then finally end up as the user who is getting the mail to drop it in his postbox.
None of the files matter there except freshclam.log That's owned by clamav:clamav, and the script cannot change it to amavis:amavis I guess.
As root, try 'chown amavis:amavis freshclam.log' and then restart.