Disable Thunderbird inline attachments

So after actually getting a complaint about it, I finally got fed up with Thunderbird sending text file attachments as inline attachments. I’d already been annoyed at GMail displaying things I sent myself inline, making it hard to copy diffs (because the amount of whitespace at the end needs to be exactly right) or easily save files.

Here’s how to tell Thunderbird to always send attachments as attachments, instead of inline:

  1. Open the Thunderbird Preferences (this is under “Preferences” in the Edit menu, or “Options” in the Tools menu, depending on your OS).
  2. Go to the Advanced section, and the General tab on there.
  3. Click the Config Editor button on there.
  4. Enter mail.content_disposition_type in the filter box.
  5. Double-click the only item in the list (with the exact name mail.content_disposition_type, obviously), and enter 2 as its value (instead of the 0 it’s on originally).
  6. Close the Config Editor with the [x], and close the Preferences with [OK].

You’re now done. Thunderbird will now send plain text files as an attachment. Any other non-binary files will still be sent inline. If you want all your files to be ‘real’ attachments rather than inline attachments, set the pref to 1 instead. Tip-of-the-hat to Marco for the tip about using 2 instead of 1.

All this information was obtained from LXR and the MozillaZine KB.

20 thoughts on “Disable Thunderbird inline attachments

  1. Yay! Yay! Now people will believe me when I say that TB displays stuff inline. Mostly, they just tell me Mail.app is broken.

  2. Why didn’t you just tell them you had it on good authority (that is, I said so) that Mail.app was just doing as it was told?

  3. Spanks alot! This explains it all!

    I’ve just made my self look really stupid infront of my boss, failing to send him an attachment like five times in a row. Now I realise that he had the attachment inline and cut off in his client.

    While spewing on Thunderbird. Have you noticed that it freezes the entire application while checking an imap-account? Every minute my typing stops for 5-10 seconds while waiting on sync. That is so annoying!

    I should just convert to a real client, but its such a hassle!

  4. very much appreciate this “bug fix” (I’ll hold that any behavior that is that undesirable is a bug), it was definitely a problem as I would (attempt) to ship source code which my recipient would have to copy & paste and report back the annoying “feature” about TBird (which I had been unaware of until then).
    So in short “I love it”, although I was not clear about the comment “If you want all your files to be ‘real’ attachments rather than inline attachments, set the pref to 1 instead…”. What is the difference between a ‘real’ attachment and an “inline attachment”, if anyone might offer up a thought?
    In short, I do like (love) TBird considerably more so than the rather “heavy” Outlook – although in my perfect world I’d have an app that would cleanly archive all my mail messages to a database so I could confidently empty my inbox frequently, there is probably one out there, so I’ll not try to duplicate it.
    Best Regards to All

  5. Thanks for the post. As of today, setting the value to 2 did not work for me, whereas setting the value to 1 did.

    I am on Thunderbird version (20090605).

  6. I am also using Thunderbird version, and it worked perfectly for me.

    Thank you.

  7. I tested setting the value to 1 and 2 and keeps loading the XML files that people send me inline… Anyone having any luck with XML’s ?? It takes like 20 sec to load an XML and no one ever sends them in a Zip ;(


  8. I’m also using Thunderbird version, WinXP (Home) with all updates.

    I thought this might be the answer to my problem, but unfortunately,
    neither value (1 or 2) works for me, even after re-installing Thunderbird !

    Such a shame…

  9. BrianB, Andy: The fix is to do with the documents you send, not the ones you receive. If people send you things inline that shouldn’t be send as such, your best bet is to ask them to configure their e-mail client better, as far as I can tell… 🙂

  10. Pingback: craschworks » Blog Archive » GEEK: How to tell Thunderbird to always send attachments as attachments, instead of inline

  11. First (joking) if it isn’t inline – is it outline?

    Second, shouldn’t the option be handled more along the lines of document types? So people could set in/out for each type of file? Default the line to always being a normal attachment but allow the user to change this selection? Thunderbird does this for other aspects of the program – attachments are just as important.

    In any event – I am so happy you made this webpage. Thunderbird just started acting weird on me. Turns out – my option was set to zero(0). 🙂 Now it is two(2). Thanks again!

  12. @BrianB, Gijs:

    Actually, there’s a setting for that as well:


    set it to false and it might take care of the issue. (for documents you RECEIVE)

  13. Another fix that is not shown. In the config editor there is a value that says: mail attachments inline – boolean- true.
    Change this value to “False”. I typed “attac” into the filter to narrow the results. This worked for my .DXF issue!

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