FutureQuest, Inc. FutureQuest, Inc. FutureQuest, Inc.
Knowledgebase: Spam/Email Filters
The Order in Which Email Filters Run
Posted on 20 November 2003 05:34 AM

FutureQuest® offers Site Owners several types of email filtering options that include SpamAssassin, Built-in filters, and Custom filters.

When a new email is delivered to an email address on a domain, filter processing will be handled as part of the delivery process on the FutureQuest® mail system. In the event that an email account has multiple filters enabled, the following shows the order in which the filters will be executed.

If any Global Filters are enabled for the domain, these run first.

Note: Global Filters affect every piece of email delivered to a domain, including its IROs and IRMs.

Global filters are executed in the following order:
  1. SpamAssassin - note that SpamAssassin may not be enabled both as a Global filter and also as a filter on individual mailboxes within the same account.

  2. Built-in Filters - in the case that more than one Global Built-in filter is enabled on a domain, they are executed in the order listed on the Global Built-in filters page in the CNC.

  3. Custom Filters - in the case that more than one Global Custom filter is enabled on a domain, they are executed in the order listed on the Global Custom filters page in the CNC.
After Global filter processing has completed, the mail system will look up the mailbox to which the email message should be delivered. This may be a specified POP account, an alias, a blackhole or the Catch-All email address.

If multiple filters are enabled on the mailbox to which the email message is finally delivered, then they are executed in the following order:
  1. SpamAssassin - note that SpamAssassin may not be enabled both as a Global filter and also as a filter on individual mailboxes within the same account.

  2. Built-in Filters - in the case that more than one Built-in filter is enabled on the mailbox, they are executed in the order listed on the Built-in filters page in the CNC.

  3. Custom Filters - in the case that more than one Custom filter is enabled on that mailbox, they are executed in the order listed on that mailbox's Custom filters page in the CNC.

If an email is forwarded to another mailbox in the FutureQuest® mail system, even within the same account, it will go through the entire delivery process again. Therefore, if the email address user1@example.com is a forwarding alias to myrealemail@example.com, then email sent to user1@example.com would be processed through any active Global Filters, then any individual filters enabled on the user1 alias; then when the email is forwarded to myrealemail@example.com, it is considered to be a new delivery process and therefore would be processed by the Global Filters again, and finally by any individual filters enabled on the myrealemail mailbox.

Note that the FutureQuest® mail system will not run SpamAssassin processing on the same email message more than once, even if it is forwarded to another mailbox in the FutureQuest® network that also has SpamAssassin enabled. The first SpamAssassin filter to score the message will insert the appropriate email headers and any subsequent SpamAssassin filters will operate on these original results.