more exactly, I still have spam coming in where I wouldn't expect it, and noticed, its mostly emails that come in for an email alias where spam seems to get through, hence my question: are mailboxes, email aliases, email catchalls and email forwards all treated equal when it comes to SPAM scanning?
Spam scanning depends on the settings that you had choosen for the domain and / or mailbox. Settings in mailboxes ovveride domain wide settings. For aliases the domanwide settings are relevant.
Spam goes thru alias email When I add some rule to content filter and I have not set any Spamfilter in domain content filter seems not work. Is this ok behavior?
I guess you mix up some things here. This thread is about amavis / spamassassin and amavis is only active when you enable it for a domain. If you mean postfix header or body filters then this is not related to amavis or enabling of amavis. If a postfix header filetsr dont work then you have most likely a syntax error in your filter regex.
