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Send attachments as real attachments

From MozillaZine Knowledge Base

This article was written for Thunderbird but it also applies to the Mozilla Suite.

Thunderbird normally sends attachments inline (as part of the message body), not as real attachments.

Some recipients will see some of your attachments as part of the message body, even if this makes no sense. For example, if you attach a plain text file, then some recipients will not see an attached file. Instead, they will see the contents of the file at the bottom of your message. If the file is encoded data, then some recipients might see garbage at the bottom of your message.

To send attachments as real attachments, set the value of your mail.content_disposition_type preference to 1. You can do this by using Tools -> Options -> Advanced -> General -> Config Editor to change the value, or by editing the prefs.js file and adding:

user_pref("mail.content_disposition_type", 1);

After you make this change, Thunderbird sends all files as attachments. Even if you paste a file into the body of an e-mail, some recipients might see it as a separate attachment. If that's unacceptable and you only have a problem with a few file types you could try using the MIME Edit extension to associate it with a different MIME type and see if that works around the problem.

Sometimes a recipient might configure their e-mail client to display all attachments inline. There is nothing you can do about that other than tell them it's their own fault.

See also

About:config (If you're not using Thunderbird)

Forwarded messages not readable

Plain text e-mail (Thunderbird)

Saving and detaching attachments

Modify Thunderbird settings

External links

Related Bugs

  • Bug 65794 – Some attachments (like text/plain, text/html) get Content-Disposition: inline (incorrect)
  • Bug 66915 – UI for changing content-disposition of outgoing attachments
  • Bug 452092 – Determine content disposition for attachments from MIME type and interaction