The Bottom Line
- Zaep AntiSpam is highly effective against spam by requiring new senders to authorize
- Can be used in a local network, configurable via a web interface
- Zaep AntiSpam automatically whitelists everybody you send mail, blacklists bogus addresses
- Zaep AntiSpam authorization via email replies can open a loophole for some spammers
- Spammers using (commonly) authorized addresses get through, too
- Supports POP accounts only and the challenging messages lack captchas
- Zaep AntiSpam is a challenge/response spam filter acting as a proxy server for POP accounts.
- Alternatively, the Zaep AntiSpam MDaemon plug-in filters all incoming mail for all users.
- Zaep AntiSpam supports multiple users and accounts via a web-based interface.
- Only mail from whitelisted senders (or mail from certain IP addresses) is allowed through by Zaep AntiSpam.
- Unknown senders are challenged to authorize by visiting an URL or sending a reply message.
- Zaep AntiSpam also whitelists all recipients of outgoing mail automatically.
- Obviously invalid or nonexistent sender addresses can be blacklisted automatically.
- Zaep AntiSpam also supports global lists to white- or blacklist senders and subjects.
- The challenge used by Zaep AntiSpam can be customized for each account.
- Support for UPnP allows Zaep AntiSpam to configure attached devices for port forwarding.
Guide Review - Zaep AntiSpam 5.1 - Spam Filter
But then not all mail is spam. By definition and experience, mail from people you know usually is not spam. So Zaep AntiSpam acts as a proxy outgoing mail server and adds all people you email to your whitelist of good senders.
What about the as-yet unknown good senders of good mail? Zaep AntiSpam treats them specially with a challenge. Unfortunately, this challenge does not require them to prove they are human, but they still have to visit a link or send an email reply to show they care and do really want to send you email.
The best thing about this solid implementation of a challenge/response spam filter is that you can set up Zaep AntiSpam for your local users (at home or at a small organization) and have their mail filtered using personal — and, thanks to challenge/response and auto-whitelisting, automatic — black and white lists.
You can also set up global white and black lists, which are overridden by user lists, of course. It's a pity that Zaep AntiSpam only works with POP accounts unless you use the MDaemon plug-in (which I recommend).
Zaep AntiSpam may suffer from the problems common to challenge/response filtering: although Zaep AntiSpam's challenging message is worded well, inexperienced users can be confused, and spammers who use whitelisted addresses can get through.