In Thunderbird I can set a signature, which can be either in HTML format or in plain text. However, I sometimes write HTML mails and sometimes plain text mails (setting the format with Shift-Click on the "Write" button).

Is there a way to specify two different signatures (one in HTML and one in plain text), and have Thunderbird automatically pick the correct one depending on the mail format?

I know that TB will convert plain text signatures to HTML and vice-versa if necessary, but this gives bad results in my case (plain text signatures converted to HTML will lack the formatting my company prescribes for signatures; and HTML signatures converted to plain text will have additional asterisks that I don't want).

  • have you looked through this site? addons.mozilla.org/en-us/thunderbird
    – DarkEvE
    Oct 9, 2014 at 11:55
  • For the record, I now use the "Signature Switch" addon for this. While it doesn't select the correct signature automatically, it at least allows to easily switch to ASCII signature.
    – oliver
    Nov 20, 2014 at 10:26

1 Answer 1


Having just run into this same issue...

HTML signatures converted to plain text will have additional asterisks

This is when you use <b> tags and the like ; Thunderbird boils them down to the same markup you can use in plain email for emphasis that it will render.

What you can do is use HTML style features that Thunderbird does not do this with ; use CSS instead of tags.


Instead of

<b>This bit is in BOLD</b>


<div style="font-weight:bold">This bit is in BOLD</div>

Doing this I found it reasonably easy to create an HTML signature file that rendered down nicely as plain text. You can even include images - if you edit your signature by editing an empty email and saving it as HTML. Drag your image into the mail from the file manager, rather than using Insert > Image, and it will be embedded as base64 rather than linked to the file, enabling you to create a standalone sig file that can be shared and edited by other users.

  • Using CSS is a nice trick - I will give it a try! Not sure if all mail clients do understand CSS, but I guess in worst case they will show the signature without formatting, which is acceptable for me.
    – oliver
    Jan 13, 2015 at 15:02

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