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E-mail sig­natur: Thunderbird

These instruc­tions will show you how to check a dig­ital e-mail sig­na­ture in Thunderbird.

Valid sig­na­ture

In Thun­der­bird, dig­i­tally signed e-mails show an enve­lope with a green seal in their headers.

The ver­i­fied sender of a signed e-mail is def­i­nitely the signer of this mail. Click on the sign to obtain secure sender infor­ma­tion, i. e. to estab­lish the signer of a mail. The sender stated in the header of the e-mail does not belong to the pro­tected area of the e-mail and can there­fore be faked.

Invalid sig­na­ture

In case Thun­der­bird estab­lishes any prob­lems when checking the dig­ital sig­na­ture, a sign with a «?» is dis­played in the header of the e-mail. By clicking this sign, you can obtain fur­ther infor­ma­tion on the error found.

Prob­lems with sig­na­ture ver­i­fi­ca­tion can be due to the fol­lowing: The sender cer­tifi­cate is invalid (i. e. expired, declared invalid or faked), or the con­tents of the e-mail were changed on their way to the recip­ient (either acci­den­tally or delib­er­ately). If there are prob­lems with a sig­na­ture, please con­tact the mes­sage sender.

E-mails can be signed just like any phys­ical doc­u­ment. The coun­ter­part for hand­written sig­na­tures in this case is called a «dig­ital sig­na­ture». Signed e-mails unequiv­o­cally con­firm the author­ship of an e-mail, i.e. they cannot be faked and guar­antee the integrity of the con­tents of an e-mail.

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