PolluStop databases must be trained for PolluStop to be able to guess what's spam and what isn't. Spam is pretty much the same on most locations, but Good mail isn't, that's why a pre-trained Spam database is provided, but not a pre-trained Good database.
Here's a few simple rules to train your PolluStop database. If you have stored spam, you should try not to use the pre-trained Spam database, but train it by yourself. You'll get better results.
Do NOT use drop mailboxes and forward addresses to perform the initial training of PolluStop. This will not give the expected results. These training methods are provided for 'fine tuning of the training once the Initial Training is completed. The Initial Setup Wizard offers you a simple way to perform the Initial Training; you can also do it using the terminal, it is even faster and provides real-time information
If you don't use the pre-trained Spam database, it is preferable to train PolluStop with spam taken from the same accounts you train PolluStop's Good DB with.
There are three email address to help the pollustop plugin, as well as two drop mailboxes. Drop mailboxes should be used with IMAP/Webmail/MAPI users. Forward addresses should be used with POP users.
Yes, of course.
While PolluStop install process is optimized for IMAP/Webmail/MAPI users, it can still be setup for POP users. Still, especially if your server is for corporate mail (if you're not an ISP) you should evaluate the possibility to transfer your users to IMAP/Webmail/MAPI. This offers more security, and especially more versatility to your users: ability to create multiple folders in their account, ability to share mailboxes with other users, server-based backup.
Of course this requires more server disk space, but the cost of disk storage is always going down, it is far less expensive than having to backup each user machine to protect their mail. And you can create CGP account/domain-level rules for spam sorting and other similar operation without having to walk to each desktop and configure a mail client.
This said, it is understandable that IMAP/Webmail/MAPI may not always be an option. In those cases, PolluStop can be configured to help those POP users.
Headers:
Return-Path: <valid_user@mydomain.com> From: Mr. El Spammer <forged_address@otherdomain.com> To: Your Name <valid_user@mydomain.com> Subject: Your meds [...]
PolluStop thinks the message comes from a local user. You don't want PolluStop to think your local users are sending spam to other local users, don't you?
PolluStop assumes you are using SMTP Auth to prevent external senders to impersonate your users. SMTP Auth is recommended in all configurations, you may want to think about enabling it.
Meanwhile, or if for any major reason you can't enable SMTP Auth, you can configure PolluStop to stop relying only on the return-path to determine where the message came from.
Open PolluStop Settings, Advanced, and enable the "Check More Than Return-Path" option, near the top of the page. When you enable SMTP Auth in CGP, disable this option.