When I try to send an E-Mail with attachment, I get the error:

There was a problem including the file filename.pdf in the message. Would you like to continue sending the message without this file?

I get no more infos about the problem. I tried several filenames (without spaces) and several mail providers. It`s always the same.

Does somebody have an idea, what this could be caused by? All threads with this error message I find are from latest 2016, and solved. But it`s december 2020, and I get that problem. Is there a detailed error log for thunderbird, where I can get more infos about the problem?


  • Where is the file stored on the machine? Could this be a permission issue, Thunderbird running as a different user as the owner of the file? What is the size of the file? Is it big? Dec 14, 2020 at 16:04
  • It`s 75 KB. And it is stored in my home directory, with rw-r-r, so should be readable for everybody. Dec 14, 2020 at 16:07
  • Are you trying to put the file in the body of the message, or is it a regular attached file? Have you tried switching to a plain-text email format? Dec 14, 2020 at 16:10
  • It`s regular attached. Switching to plain-text does not solve the problem. But I found out, that it happens not for all destination email adresses. Is there a detailed error log in thunderbird somewhere? Dec 14, 2020 at 16:16


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