Spam is a BIG headache for us. We have users that have had their email addresses posted on a website for years. They are on every spammers email list and they cannot change their address. Some of them receive 90% spam.
The spam filters, like spamassassin, that are included with Zimbra do a great job filtering spam but they don't get everything. We setup a set of filters that do the following:
1) If the From address is in their contacts list, the mail is left in the INBOX.
2) If the From address is not in their contact but the mail is addressed to them, the mail is moved to possible spam.
3) If the From address is not in their contacts and the mail is not address to them, its moved to the Junk folder.
We have added an exception to allow mail that claims to be from our domain. That allows all inter-office mail to stay in the INBOX but it also allows a small amount of spam through daily.
My users have forgotten just how much spam they used to receive and are now complaining about these few emails.
Now my question: Can you have a filter that looks for email address in the GAL? I would like to check the veracity of the From field. If they claim to be from our domain, but that address doesn't exist in our domain the email should be tagged as spam.
Thanks for your assistance.