Thunderbird plugin to show unmangled original URLs in place of mangled 'Safe Links' from the Office365 mail server.
Users of Office365 whose company or email provider have enabled 'Safe Links' will receive emails in which all URLs have been modified so as to redirect them via a Microsoft 'safe link' server before opening. This allows Microsoft to (at least potentially) intercept unsafe links after they have been clicked (see here, but also gives Microsoft the opportunity to log all email clicks, which some users will find undesirable.
For example, with Advanced Threat Protection', a link to
http://phishingsite.fake.ru/you/are/hacked.php
will be modified to become something like the following
https://emea01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fphishingsite.fake.ru%2Fyou%2Fare%2Fhacked.phpdata=02%7C01%7Csender.mail%40domain.tld%7C8177af7905a4406ecae208d5dc1fb7c9%7C87c50b582ef2423da4dbaedde7c84efcfa%7C0%7C0%7C63453351150545403&sdata=Te0O1xGxxxULxdzbxQ%2xxxyql2QjTt4Ken%2F00JB%2BV%2FPUA%3D&reserved=0
Although this provides potentially increased safety for users, it greatly worsens the appearance of many emails, especially plaintext emails, since Safe Links links are much longer than the originals, and furthermore it is no longer immediately obvious what site they link to.
If you prefer to only correct the cosmetic issue of the appearance of the link in plaintext email, you can set prefUnmangle to false. In this case, Safe Links will still be passed through the Microsoft server. If prefUnmangle is true, links will be unmangled to point to the original URL, which means that the Safe Links functionality is disabled.
For an overview on writing Thunderbird Plugins, see the Hello World example and MailExtension API documentation.
The plugin can be installed from Thunderbird Add-ons
Source code can be obtained mbattersby/unmangleOutlookSafelinks. To use the source code directly in Thunderbird, see the instructions in the Hello World example.
- Version 3.1.0: implements
prefUnmangleto allow text to be unmangled while preserving Safe Link targets. - Version 3.* is compatible with Thunderbird 78+
- Version 2.* is compatible with Thunderbird 68+
- Version 1.* is compatible with Thunderbird 60.*
- Original version by mib@post.com
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