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How to set up some additional Spam filters

Dealing with Unwanted Email

Our mail servers have software running on them to help combat the ever growing nuisance of spam. Every incoming message gets a "spamminess" score based on a variety of factors that most humans wouldn't ever think about. When the score a message accumulates becomes high enough (6.6 in our case), our server marks it as Spam and puts it in the recipient's Junk folder. However, to avoid any interference with the receipt of legitimate mail, we keep our thresholds pretty conservative, so you may still receive a number of messages in your Inbox that you don't want.

Fortunately, there are some extra measures you can take to be more aggressive in what you treat as Junk. The easiest thing to do is set up Mail Filters in the Zimbra webmail interface. Filters created here work regardless of how you check your email -- e.g., via the web or with an email program like Thunderbird. And they work no matter which computer you're using to access your mail, making them more flexible than client-based filters.

You can configure these filters for yourself or, if you prefer, you can submit a workorder to request that we configure them for you.

Remember to check your Junk folder periodically, especially after first instating these rules, to be sure you aren't filtering out any messages you want. As shown, these rules won't automatically discard messages. However, the contents of your Junk folder will be purged once they get to be 30 days old.

#1 - Look for messages by spam score.

1. Login to webmail at http://webmail.sas.rutgers.edu.
2. Click Preferences and then click Filters under the Mail category in the left pane.
3. Click New Filter.
4. Give the filter a Name (e.g., Spam) and leave "any" in the first drop down box.
5. For the conditions test, choose Header Named from the drop-down menu and enter the text "x-spam-level" (no quotes). Then select "contains" and enter four asterisks (****) in the following text box.

*Note: the number of asterisks represents the base spam score our server assigned to the message, which is stored in the x-spam-level header. The fewer the asterisks, the lower the spam score. Since our server's default threshold for marking a message as "spam" is over 6, this rule is more aggressive than the server's default behavior: it means you want to treat messages with lower spam scores (less "spamminess" as rated by the server) as Junk. To be more cautious, you could try five asterisks instead of four. However, experience has shown that using four asterisks usually works well.

6. For the actions section, choose "File into folder" and use the Browse button to find and select your Junk folder. Leave checked the "Active" and "Do not process additional filters" checkboxes and click OK. See below for an illustration of these settings.

Zimbra screenshot: Adding filter for Spam

 


 

#2 - Look for specific character sets. This may be useful, for example, for people who do not wish to receive Cyrillic (aka "Russian") messages.

1. Login to webmail at http://webmail.sas.rutgers.edu
2. Click Preferences and then click Filters under the Mail category in the left pane.
3. Click New Filter.
4. Give the filter a Name (e.g., Cyrillic-charsets) and leave "any" in the first drop down box.
5. For the conditions test, choose Header Named from the drop-down menu and enter the text "content-type" (no quotes). Then select "contains" and enter "koi8-r" (no quotes) in the following text box. Click the "+" symbol to add a similar rule for the "windows-1251" content-type header. (If you're wondering, koi8-r and windows-1251 are two common Cyrillic character encoding schemes.)
6. For the actions section, choose "File into folder" and use the Browse button to find and select your Junk folder. Leave checked the "Active" and "Do not process additional filters" checkboxes and click OK. See below for an illustration of these settings.

Zimbra screenshot: Naming the filters, Click the + button near the right of the window

 


 

#3 - Look for a subset of specific characters. This may also be useful for people who do not wish to receive Cyrillic messages.

1. Login to webmail at http://webmail.sas.rutgers.edu
2. Click Preferences and then click Filters under the Mail category in the left pane.
3. Click New Filter.
4. Give the filter a Name (e.g., Cyrillic) and leave "any" in the first drop down box.
5. Set up the conditions as they appear below. There are several checks that can help detect this type of message. The tricky part is specifying characters that aren't easy to type on a non-Cyrillic-based computer. To input these characters, copy and paste them from here: и л д п я. Of the characters that are unique to Cyrillic, these are the most common. (Also relatively common are ы and б.)

*Important: be careful to leave "any" in place next to the If statement. Using "any" instead of "all" means that any single one of the conditions you specify will catch the message. Using "all" would instead catch only messages where each and every one of the conditions was true -- making it much less likely to detect such messages. Also, you may be tempted to use Body instead of Subject checks for these characters. Don't -- the current filtering system will only successfully detect these characters if you tell it to look at the Subject. This limitation is disappointing but the approach is remarkably effective nonetheless.

6. For the actions section, choose "File into folder" and use the Browse button to find and select your Junk folder. Leave the "Active" and "Do not process additional filters" checkboxes checked and click OK. See below for an illustration of these settings.

Zimbra screenshot: Include "any" on the top left instead of "all" to specify the messages

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