- Do you see the same issue in Firefox, or any other browser? - Are there any add-ons installed in Thunderbird, and if so, did you try Help > Restart with Add-ons Disabled (aka Safe Mode)?

If the issue is Thunderbird-specific, an add-on could be out of date and cause it, and the issue may not occur in Safe Mode. Return to normal mode by restarting Thunderbird, go to the Add-on Manager (Tools > Add-ons), unselect Get Add-ons in the top left and click the cogwheel in the top right to choose Check for Updates.

Also have a look at this article. It’s for Firefox, but the settings apply to Thunderbird as well. Pay attention to the section about resetting printer settings in particular. The about:config entry is accessible via Options > Advanced > General tab > Config Editor.

Does this help?

Thank you very much for your recommendations. Unfortunately, I tried all of them but could not fix the problem. See the attachment.

Do you have other suggestions ?

Thank you in advance Jean-Marc Morel

I wonder if you have a corrupt font in Windows. Windows key + R then type fonts and press enter.

Is there a font that look like it is not displaying correctly? I would start looking at calibri and tahoma

Are you sure you haven’t got the mnenhy add-on installed, or perhaps you previously had and uninstalled it? I ask because the display looks prety similar to the ones shown in other issues with mnenhy (like this one), and after upgrading a Thunderbird version. This add-on is known for changing the headers of a message, which is what you seem to experience right now, AND it hasn’t been updated lately IIRC.

Perhaps you should take a look at this tread - be sure to collapse all messages and read them. There you will also find the suggestions to reinstall the printer driver (or update it, and NOT let it update by Microsoft’s driver) and to reset the operating system’s fonts, which is close to what Matt suggested. Again, if you did have the mennhy add-on installed (or some other one able to change email headers), uninstall it first to see if that helps.

Thank you Matt for your suggestion but I checked all fonts , and none appears strange and similar to what I get when I print an email header.

Thank you Tonnes also. Unfortunately I don't have the Mnenhy add-on installed and don't think it has been installed and then unsinstalled because my windows 10 system, Thunderbird 45.6, and my printer too (Epson XP-540) are recent (computer bought last October). The only add-on I have is Lightning. I did read the tread you mention but all discussions date back to 2010 and address older versions of windows and Thunderbird.

As the problem shows up not only when I print on my printer but also when I use the 'Microsoft Print to PDF' option, and only when printing email header with Thunderbird, I do think the problem is with Thunderbird but what other check and action should you suggest.

Thank you in advance for your help. Jean-Marc Morel

I'd like to add that it appears to be using a monospaced (fixed width) font for your headers, so it won't be Calibri or Tahoma. I'd check which monospace font is selected for Thunderbird.

Tools|Options|Display|Formatting→Advanced

and then check how that particular font performs when printing.

As a test, what happens if you print from Notepad, which (probably) also uses a fixed width font?

You may improve matters by using an add-on to manage your printing, such as this one:

https://freeshell.de/~kaosmos/printingtools-en.html

"it can use a font family and a font size in printing messages (for the whole message or just for headers);"

Wonderful. I installed the printingtools add-on and it solved the problem. Thank you very very much for your help. Best regards Jean-Marc Morel