MacInTouch reader Bill Benson posted a rule in the .Mac section of that site yesterday which will catch much of the current “image spam” plague.

He noticed that the image spam emails always have two distinguishing marks: they come from a different address each time and the Content-Type header begins with “multipart/related”.

So a rule that matches both those conditions like the one below will snag them before they hit your inbox:

The only tricky thing here is selecting the “Edit Header List…” from the list of conditions and then entering “Content-Type” in the next window. “Content-Type” will now appear in the list of conditions. You will need to select it and enter as its content “multipart/related”.

You might choose to replace the “Not in my previous recipients list” condition with “Not in my Address Book” depending on your own correspondence patterns. Adjust to suit your own tastes.

There is a small downside. It seems likely that this rule will move some “false positives” into the Junk folder. But checking that from time to time is much better than wading through the image spam that Mail.app’s Junk filter is currently missing.

UPDATE: It will be easier to spot any false positives moved by this rule, if you add a “Set Color of Message” action to it, choosing a unique colour. That will help them stand out in an overstuffed Junk folder.spam, junk, image spam, stocks, mail.app, apple mail, rules

German blogger Jan Hinze was surprised to discover that his Junk Mail folder had gathered 41,124 items of junk mail in the past four months:

He had no idea that Mail was at work behind the scenes, keeping this stuff out of his Inbox.

As well as winning the intra-office competition for the largest mailbox, he offers “hefty praise” to Mail.app’s junk filter, which could so easily recognise and master this amount of spam, even on a clapped-out G4 PowerBook.spam, apple mail, mail.app, junk, filter

At Betalogue, Pierre Igot reports two more annoyances in Apple Mail:

1. Mail 2.0: ?¢‚ǨÀú0 messages, 3 unread?¢‚Ǩ‚Ñ¢ — By doing several complicated things at once, he brings Mail.app‘s multi-threading ability to its knees.

   It shouldn’t happen, it shouldn’t be so hard to discover that the app has stalled and it shouldn’t be so difficult to unstick it.

   This leads to some reflections on how Mail.app might be better designed so that things like this are more transparent for average users.

2. Mail 2.0: ?¢‚ǨÀúUndo Mark as Junk?¢‚Ǩ‚Ñ¢ doesn?¢‚Ǩ‚Ñ¢t undo anything — Pierre has an email incorrectly-marked as Junk. If the Junk filter is on automatic, it will move the message to the Junk folder.

   But going to the Junk folder and selecting the message to “un-junk it”, he notes that clicking the “Undo Mark as Junk” option in the Edit menu or selecting “Mark as Not Junk” from the Message menu doesn’t do anything.

   I can’t reproduce this behaviour. When I do this, the message does get “un-junked”. And I guess that Apple Mail’s Spam database is updated in the background, but I agree it would be useful if Mail.app automatically restored the message to the mailbox from whence it came. (like Entourage does…Grrrr!!)

As always, excellent holiday reading!

SpamSieve is a third-party spam catcher that supplements Apple Mail‘s inbuilt filter. It uses Bayesian filtering technology, which differs from Mail.app’s own system (see “How Apple Mail’s Junk filter works?”).

A updated version (2.4) was released today, featuring the following major improvements:

• Made various changes to the Bayesian engine to improve accuracy.
• Added some heuristics for detecting phishes.
• Apple Mail messages can now be filed into different mailboxes based on how spammy they are (requires 10.3 or 10.4). (Read more about this new feature)
• The Apple Mail plug-in is now a Universal Binary, so SpamSieve can be used on Intel-based Macs without running Mail in Rosetta.

You can read the full Changelog on the SpamSieve web site.

SpamSieve is shareware (USD 25) and is available from the developer’s web site.