Richard Gunstone - Blog

Using Imapfilter (the swiss army knife for IMAP mailbox management) (Misc)

Imapfilter is one of the more useful email management tools available on Linux. Using Imapfilter, you can connect to remote IMAP mailboxes and perform queries and take actions based on user-customisable filters. Periodically running Imapfilter allows simple processes to be implemented. The commands it is able to perform on a remote mailbox include delete, copy, move, flagging.

An interesting feature of Imapfilter is the capability to maintain connections to multiple IMAP mailboxes at the same time, and take actions between remote mailboxes.

Imapfilter is configured using the Lua programming language and specified in the config.lua file usually located under /home/user/.imapfilter folder.

Some of the example queries that can be sent to an IMAP mailbox include:

• Select all messages in the folder
• Is the email new?
• Is the email recent?
• Is the email larger than a specified value?
• Is the email older than a specified value?
• Does the email have a specific flag set?
• Did the email arrive before a specified date?
• Does the email have a subject containing a specified string?
• Does the email match a string within the message body?
• Is the email from a particular sender?

For example, using Imapfilter the following activities could be performed:

• In a customer service mailbox scenario, you could pre-filter emails containing a customer reference prefix into separate team mailboxes.
• Emails from a specific domain could be quarantined into a separate mailbox.
• Emails could be archived off into a separate mailbox.
• Large emails could be moved to another mailbox having a greater storage quota.

One potential use case is managing legacy mailboxes: by migrating emails directly using Imapfilter, one can easily avoid the pitfalls of some of the common alternatives. For instance, repeated polling using some webmail solutions can leave original messages behind, decreasing available quota until the mailbox reaches capacity.

Here are some examples of config.lua and further discussion of use cases and example code:

https://fossies.org/linux/imapfilter/samples/config.lua

https://raymii.org/s/blog/Filtering_IMAP_mail_with_imapfilter.html