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Remote Content By Folder 2.0
Decide whether to allow or block remote content in messages by comparing the names of the folders in which they are located to configured regular expressions.
About this Add-on
If an email message contains a link to remote images in it, then by default Thunderbird blocks the remote images and displays a banner with a button you can click to display the images and optionally add messages like this one to a whitelist so images will be displayed automatically.
Alternatively, you can change your Thunderbird preferences so that remote images are displayed by default, except in messages that Thunderbird thinks are spam; remote images are blocked with the banner in those even if you enable the preference to display remote images by default.
I wrote this add-on because I want slightly different behavior: I want Thunderbird to decide whether to display or block the remote images in a message based on what folder the message arrives in.
Here's are some examples configurations (configurations for the add-on are added in its add-on preferences):
Allow regexp: .*
Block regexp: ^(Spam|Trash|Deleted (Items|Messages))$
Check block regexp first: yes
In extended regular expressions, the kind used here, a period matches any single character, * after anything means to match zero or more copies of that thing, ^ matches the beginning of the string, $ matches the end of the string, and parentheses and vertical lines are used to group alternatives. Therefore, what the configuration above says is, "Block remote images for any messages that arrive in folders named Spam, Trash, Deleted Items, or Deleted Messages, and display remote images for messages that arrive in any other folder." Note that rather than using .* as the allow regexp, I could just as well have used ^ by itself, which would mean, "Match any string which has a beginning," which means any non-empty string (obviously folder names are not empty).
Generally speaking, to list any arbitrary set of folder names in the "Allow regexp" or "Block regexp" setting, do the following:
- Start with ^ to indicate the beginning of the string.
- Next put ( to begin the list of folder names.
- List the folder names separated by |, but put a backslash (\) in front of any symbol in a folder name, to ensure that it isn't treated as a special regexp character.
- End with )$ to mark the end of the list of folder names and the end of the string being matched.
Note that the settings you specify for Remote Content By Folder are only applied when the message first arrives. If you change the settings Thunderbird won't go back and re-evaluate whether to display images for existing messages, and if you move or copy a message from one folder to another Thunderbird won't re-evaluate whether to display images based on the target folder.
Similarly, this only impacts messages for which the question, "Should remote images be displayed?" has never been answered before. So if Thunderbird decides to block images in a message and puts up the banner, and then you tell it to display the images in that message, that will stick even if the message is in a folder that Remote Content By Folder thinks images should be blocked in.
There are some remaining open issues. See https://github.com/Extended-Thunder/remote-content-by-folder/issues to view them or to report any additional issues that you find.
- Source code released under Mozilla Public License, version 2.0