Fighting Spam

Fighting back spam with PowerMail 5: a primer

One of the most important features of PowerMail 5 is its inclusion of tools to efficiently combat spam. 

For best efficiency, you will be best off knowing thy enemy (i.e. which messages are offending) and your friends (i.e. people in your address book). Regardless of your particular situation, we have tried to make the setup process as simple as possible.

Design philosophy

  • Minimize the risk of not seeing mail that might have been treated as spam: this requirement implies actually fetching mail messages, even partially, in order to process them.
  • Be tolerant about mistakes and allow reversibility: no spam filtering scheme is perfect; false positives (good messages marked as spam) and false negatives (spam marked as good messages) inevitably occur
  • Open to the most appropriate solution for each user. PowerMail 5 offer new filter features that do a decent job at weeding out with moderate spam. If spam has already become a major pain for you, PowerMail will do stellar job at integrating third-party tools such as SpamSieve™.

The basic approach is an detailed extension of PowerMail's filters; first, one needs to determine whether a message looks like spam or not. If so, any number of actions can be applied to it.

Additional functionality allows the user to correct errors, and even teach smart filters such as SpamSieve ways to improve future sorting.

New spam-related features

Spam rating database field and list column 

PowerMail 5 stores a rating between 0 and 100 for each message. This rating is either assigned via filters or manually. This rating can be displayed as a bar graph in message lists by clicking the appropriate checkbox in the View Options dialog

Additional filter conditions

Spam rating 

PowerMail can take action based on a message's spam rating being equal or higher to a given value; this is typically determined by a third-party tool such as SpamSieve.

HTML part filter 
This allows detection of HTML parts in messages; as good e-mail etiquette suggests that HTML messages are to be sent with a plain text part as well, this condition allows the creation of mutually exclusive filters. When a message is found ONLY to have an HTML part, the message gets a rating of 50 and this rating can be further incremented or decremented by the raise/lower spam rating filter action (see below) 

Subject/body contains at least one of the words 
In order to fine-tune your manually-definded filters, it is now possible to filter based on the inclusion of one of a list of words (i.e. "wholesale Viagra guaranteed Windows inches medication pharmacy mortgage" in a single filter.

Number of recipients is 
Spam messages tend to have no recipients set, while unwanted announcements can have large recipient lists; this condition can be useful alongside others. 

Attachment name 
Windows executables (.exe) or picture files (.pif) are some of the preferred vectors for viruses; PowerMail 5 now offers the possibility to filter on attachment names so as to further characterize unwanted messages.

AppleScript as filter condition 
Before PowerMail 5, a filter could only specify an AppleScript as an action; now you can also have scripts which operate as filter conditions, which means that in certain cases or all cases you can have an AppleScript become your fully customizable filtering system, with PowerMail executing whatever action (built-in and/or another AppleScript) you choose.

Additional filter actions

Evaluate spam rating 

Depending on how the assistant configured your filter, this action will either call upon SpamSieve or rely on the server-set X-Spam headers to assign a spam rating to a message

Raise / lower spam rating 
This action allows either to raise or lower the spam rating for a given message

Spam assistant

To make the setup experience as painless as possible, PowerMail 5 includes an assistant that will set up all the necessary spam filtering for you.

Spam preference pane

This is where you define what exactly happens upon marking a message as spam or as good. 

If you are upgrading from PowerMail 4 and were using SpamSieve before:

PowerMail will automatically disable those filters which made use of the AppleScripts which used to be necessary to integrate SpamSieve.

When using SpamSieve, the sensitivity slider is disabled, as all of the evaluation work is done within SpamSieve itself; options are to be set within the SpamSieve user interface.

When creating spam filters, the spam assistant will place them at the top; you can, and probably should re-order your filters in the following order:

  1. known good messages (work domain, mailing lists, usual newsletters): This way, messages that might look to SpamSieve as spam (such as newsletters and mailing list traffic) that you legitimately want to receive will be processed first by your custom filters; don't forget to add a "stop processing this message" action at the end of such filters 
  2. spam-related filters So as to move spam out of the way before going on with filtering 
  3. all other filters If you've setup filters for dealing with spam before, we recommend that you disable the "Apply to incoming messages" checkbox for each of them before starting. Eventually, you will be able to delete them entirely. 

Another thing you may want to do is clean up your address book by deleting known senders of spam from it, and adding likely senders of good messages. If you have a list of messages whose senders you would like added in one go, create a special filter with the "add to address book" action applied to all messages, then select the messages whose senders you want added and use the appropriate "Perform filter" menu item to them. Once you're done, make sure that you disable or delete this filter, as all senders will otherwise be added. 

Using PowerMail with X-Spam headers

If your ISP's mail server features server-side rating of spam, we encourage you to use this option in the Spam Filter assistant, as PowerMail can use the server's rating (indicated in X-Spam style headers) in order to set qualify fetched messages.

Using PowerMail with SpamSieve

PowerMail and SpamSieve versions 2.1.3 and greater are fully integrated. In order to train SpamSieve, just select messages and use the "Mark as Spam" and "Mark as Good" features, which will both train SpamSieve and enhance its corpus as well as internally qualify these messages in the PowerMail database.

Customize your toolbar

You can change the order in which the "Mark as Spam" and "Mark as Good" buttons are displayed in your toolbar for Recent Mail or Mail Browser windows (or both).


Why isn't there a "bounce" feature ?

Some mail clients offer a "bounce" feature, which creates a message to the sender that pretends to be a server-side rejection. In our experience, we have found tha t spammers actually derive some useful information about this and things actually get worse - thus our choice not to include this. This can however be performed using an AppleScript if needed.

What does the "addressed to full name" option do ?

This will try to match the RFC 822 address for received messages to include all of the words (even if in a different order) that are in the Real name field in the fetching account's Identity pane

How do "X-Spam" headers, such as those inserted by SpamAssassin-equipped servers, influence a message's Spam rating ?

PowerMail will give a spam rating of 5 points for each star (*) in the X-Spam header up to 10 stars. This can be combined with a filter which raises or lowers the spam rating based on other factors and/or with the filter action which determines whether an HTML part is present.

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