Mail Filtering, Forwarding, and Spam Reduction

Regardless of whether you wish to use a standalone mail client for reading your mail, or you want to use the webmail interface, or you prefer to have your mail forwarded elsewhere, all such configuration must be done through the webmail interface (Horde). Even if you do not use the webmail interface to read your mail, it is the only mechanism that can be used to configure the mail filters.

Note that these filters will be active regardless whether you use the webmail interface, a standalone email client, or forward your mail elsewhere.

This document gives some hints on some of the most common things to change related to filtering and forwarding. Horde capable of much more, so you are encouraged to peruse your configuration and experiment.

• Filter Introduction
• Recommended Anti-Spam Filtering
• Other Filtering
• Forwarding Mail to Other Addresses

Filter Introduction

In order to access your filters, perform the following steps:

1. If you have not already done so, log into the Webmail interface.

2. On the left of the page you will see an Mail menu item. Click on the plus icon to expand it if necessary.

3. Click on the Filters item under Mail

4. The default rules consist of the following:

   • Whitelist Mail from addresses on this list will always be delivered to your mailbox.

   • Vacation This rule is disabled by default. If enabled, people who send you email will get an automatic answer. Traditionally this was used to send back a message to the effect of "I'm away from my email for a while, I'll respond to your message when I return". Before you enable this, consider whether or not you really want people to know that your residence is vacant for an extended period. Ensure that you do not send replies to mailing lists or you can cause a mail loop. Depending on the mail list, this may result in your mailing list subscription getting cancelled and/or your email account to be disabled. Ensuring that the Do not send responses to bulk or list messages remains checked will handle most mailing lists.

   • Blacklist Mail from addresses on this list will be always be handled as specified. The default action is to delete the message, but the action can be changed by editing the blacklist rule.

   • Spam Filter This rule is disabled by default. It is a shortcut to that can be used to redirect spam to a spam folder. If you wish to enable it, you must specify a destination mailbox when you edit the rule or it will be ineffectual.

     Please do not enable this rule if you are forwarding offsite and not intending on accessing your mailbox on this site on a regular basis.

   • Forward This rule is used to forward all remaining email to another address. Please do not enable the Keep a copy of messages in this account unless you ensure that you are periodically deleting mail from this server; This will keep mail usage to ballooning out of control and the subsequent enforcement of mail quotas.

Recommended Anti-Spam Filtering

The following are recommended changes to your filtering to minimize the amount of spam you receive, without introducing a significant chance of accidentally deleting valuable email.

1. Move the Vacation rule to after the Blacklist and Spam Filter rules by using the down arrow at the right end of the Vacation rule. This will ensure that if you blacklist someone, you won't be sending them vacation messages.

   As you add rules, the Vacation rule should remain below any other antispam rules, or rules that deal with mailing list traffic (if, for example, you sort mailing lists into alternate folders).

2. Enable the Spam Filter rule by clicking on it, selecting the folder that should receive possible spam (it is suggested that you use your Spam top level folder) and then click Save and Enable.

3. Add in a Discard Spam Rule:

   • Click on the New Rule button.

   • In the Rule Name field enter "Discard Spam"

   • In the Select a field drop-down list, select Self-Defined Header from the bottom of the list (you might have to scroll down). Wait briefly for the screen to redraw.

   • In the empty field under the Self-Defined Header box, enter X-Taiga-MailScanner-SpamScore

   • The drop-down box to the right of the Self-Defined Header box should remain as Contains.

   • In the empty field to the right of the Contains box, enter six s characters: "ssssss" (without the quotes). The number of s characters perform the same function as the score value of the Spam Filter rule that was initially provided in your filter set.

     If you want to automatically delete more spam at the risk of also deleting non-spam messages, then reduce the number of s characters.

     If you want to be more cautious about not deleting non-spam message, increase the number of s characters in the rule. The downside is that you will have to manually delete more spam this way.

     The number of s characters should remain more than in the Spam Filter rule described above.

   • You may ignore the additional Select a field drop-down box; it is used to create more complex filter rules.

   • In the Do this drop-down box select Delete message completely.

   • Click on the Save button.

   • Move this rule up so that it is below the Blacklist rule and above the Spam Filter rule by entering the number of the Spam Filter rule in the To box at the right end of the rule and pressing your enter/return key (or use the up arrows).

Other Filtering

You may use this filtering interface not only to control spam, but also to pre-sort your inbound mail according to various criteria. One common kind of rule is to sort mailing lists into their own mailboxes. You need to first create the destination mailbox under your main mailbox. In order to facilitate sorting, most reputable lists will have either a Sender or List-Id header that is suitable for the purpose. For mailing lists, filtering based on the Subject does not always work, and filtering based on the From field rarely works.

Forwarding

This server allows forwarding of your mail offsite. If you decide to do so, please note the following:

1. Please do not retain mail on this server unless you plan to use it or periodically delete it. This is especially true for antispam rules that just file the spam into another mailbox.

2. It is suggested that you set up a "delete" rule for high scoring spam as described above in Recommended Anti-Spam Filtering. Not only will this reduce network bandwidth, but it lessens the chance that the destination site will blacklist this server.

The only supported mechanism for setting up mail forwarding is via the filter rules in the webmail interface. Specifically, the old method of creating .forward files will no longer work.

In order to set up forwarding:

1. If you have not already done so, log into the Webmail interface.

2. In the left panel, click on Mail to expand it.

3. Under Mail in the left panel, click on Filters.

4. Once the main panel redraws, click on Forward.

5. Enter the addresses (one per line) to which the account's email should be forwarded. Click Save.

You can enable/disable the forwarding rule from the main Filters page.