DomainKeys Identified Mail (DKIM) is a method which allows domains to sign e-mails. The add-on verifies these DKIM signatures and shows the result in the e-mail header. This way it is possible to see which domain is claiming responsibility for a specific e-mail. How the result is shown can be changed in the options.
It is important to note that an e-mail can be signed by an arbitrary domains. A valid DKIM signature alone is therefore not an indicator for a trustworthy e-mail. Always check who the signer is to determine if an e-mail is trustworthy!
In some cases, the absence of a DKIM signature can be useful to identify scam e-mails. If it is known that a certain domain is signing all its e-mails with DKIM, the absence of a DKIM signature is a strong indicator for a forged e-mail.
To ease the checking of if and by who an e-mail is signed, the add-on supports the use of sign rules. With sign rules it is possible to specify that e-mails from a certain sender have to be always signed by a specific domain (also referred to as SDID). More about sign rules at https://github.com/lieser/dkim_verifier/wiki/Sign-rules.
A description of all the available add-on options can be found at https://github.com/lieser/dkim_verifier/wiki/Options.
The add-on can be downloaded from https://addons.thunderbird.net/thunderbird/addon/dkim-verifier/ or https://github.com/lieser/dkim_verifier/releases. The source code is available at https://github.com/lieser/dkim_verifier
Support and Bug reports
The preferred way to report bugs is by creating an issue at https://github.com/lieser/dkim_verifier/issues.
If debug information is needed, enabling of debugging in the advanced options is sufficient in most cases. Details about the available debug options can be found here.
How to Contribute
The easiest way to contribute is to report every error you encounter. Ideas for future enhancements are also welcome.
Another good way is to contribute to be default sign rules and the included favicon list. Note that E-Mail providers will not be added to the favicon list.
In case you are interested in providing a new translation (or improving an existing one), you can do this by either creating a pull request on github or via BabelZilla (http://www.babelzilla.org/forum/index.php?showtopic=7543).
Also feel free to fix bugs or add futures yourself by creating a pull request. For bigger changes best contact me first for better coordination.