Rated 3 out of 5 stars

It wrote:
"DKIM: Message is not an e-mail"

This review is for a previous version of the add-on (0.4.2). 

Fixed in version 0.4.3

Could you please provide more information, so I can try to fix this?
Best at https://github.com/lieser/dkim_verifier/issues, http://forums.mozillazine.org/viewtopic.php?f=48&t=2704121 or by e-mail to dkim.verifier.addon@gmail.com.

Here some of the Information that would be helpful:
Does this happen with every e-mail, or just one?
If you enable debugging in the options, is there an error message that says “Message is not in correct e-mail format”?
If you now how to, can you look in the profile folder which line ending (LF or CR+LF) is used for the e-mail?
I assume you are using version 0.4.2 of this add-on?

If you have an e-mail without personal information in it, to which this happens, it would also be nice if you could save it (right click and “Save as...”, or in the header “Other Actions” and “Save as...”) and send the file to me, so I can test it my self.
But if you answer all additional questions what appear during testing, it's probably not necessary.

Thanks.

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Edit:
Problem fixed in version 0.4.3.