When I compose and send an email (I always write plain-text emails) in Thunderbird, it always truncates my sentences and adds line breaks in the middle of my sentences.

How do I turn this feature off? It is quite annoying to me.

For instance, when I send people long URLs, the URL gets cut in the middle because of the automatic line breaks.

I am using the latest Thunderbird 9 for Mac OS X

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    I would have upvoted but no research effort was evident. – null Jan 4 '18 at 3:20
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    @nslntmnx Sometimes it may be unclear even where to start researching. – Dr_Zaszuś Apr 23 '18 at 11:15
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    I am doing research, and this question is what I get... – onlycparra Aug 11 '20 at 7:04


Disable word wrapping in outgoing messages

  • Edit -> Preferences -> Advanced -> General -> Config Editor
  • Set the preference called "mail.wrap_long_lines" to false

See also: http://kb.mozillazine.org/Plain_text_e-mail_(Thunderbird)#Flowed_format

... mail.wrap_long_lines to control the wrapping of long lines (defaults to true)

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    This did not work for me until I toggled mailnews.wrap_length to zero as well. Then it worked like a charm, even with wrap_long_lines to false. This answer did point me towards the Config Editor, which is a good thing. – Joost Aug 12 '13 at 13:36
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    Moreover, I had to close and re-launch TB to make it notice the new setting. For the record, this happened with TB 24 under Ubuntu 12.04 x64. – Marcello Romani Mar 11 '14 at 12:44
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    It's enough to close the mail window (save as draft, close and reopen if you do not want to start over). – fuenfundachtzig Jul 23 '14 at 9:42
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    @Joost, setting the "mailnews.wrap_length" to 0, actually did fix it for me. Thanks. – Vicer Mar 3 '15 at 22:17
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    As of Thunderbird 45.1 or earlier, the mailnews.wrap_length setting is now called mailnews.wraplength. – tanius Jan 20 '17 at 21:31

Setting mailnews.wraplength to 0 disables wrapping on compose window, but as a side-effect does not wrap sent messages.

I addressed this problem by setting:

mailnews.wraplength 0
mail.compose.wrap_to_window_width true
plain_text.wrap_long_lines true
view_source.wrap_long_lines true
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    Can you give an example of how it doesn't "wrap sent messages"? I'm wondering if I should use your settings or the basic mailnews.wrap_length version. – Paul Oct 25 '15 at 16:25
  • Was there a typo in this answer? In Thunderbird 45.1.0 there's mailnews.wraplength but not mailnews.wrap_length – Graham Perrin May 22 '16 at 11:22
  • I have amended the answer to use mailnews.wraplength – Freeman May 30 '16 at 5:57
  • It may work for you, but you reported some settings that say the exact opposite of what is asked. This smells like cargo cult. – ceztko Feb 20 '18 at 0:00

For me, the accepted answer did not show any effect.

As Joost pointed out in his comment, the correct solution is setting

mailnews.wraplength → 0

in the config editor (Edit → Preferences → Advanced → General → Config Editor...).

  • I think this should be an answer on its own, as Joost's comment might be overlooked and Freeman's answer adds more settings that are unnecessary for the addressed problem. – Scz Mar 24 '17 at 13:21

There is also an addon that can be used to disable the wrapping without messing with the configuration editor:


With this addon the wrapping can be toggled with CTRL+SHIFT+W (the message must be started in text mode, it doesn't work in HTML mode).

  • With Thunderbird 45.1.0 on KDE on PC-BSD 11.0-CURRENTMAY2016 I can enable that add-on but the resulting menu option is greyed out. – Graham Perrin May 22 '16 at 11:23
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    @GrahamPerrin Probably because you are in HTML mode (or switched to Text mode from the HTML mode after opening the new message) – Emmanuel Bourg May 23 '16 at 7:53
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    OK, the underlying problem may be that I have never successfully got plain text by default. I might find a workaround/fix for that elsewhere. Thanks. – Graham Perrin May 25 '16 at 16:59

Concerning URLs, it is actually sufficient to enclose them in < and >.

  • @chipperyman573 Question title: "Tell Thunderbird not to [...] wrap lines" question body "for instance [...] long URLs". One answer: put it between < and >. Not as good as the accepted one, yet a lot quicker and also working if you prefer to have the remaining text wrapped – Tobias Kienzler Feb 16 '14 at 8:04
  • Yeah I misread the answer, sorry. – Jon Feb 16 '14 at 8:08
  • @chipperyman573 no worries, I guess you saw it in the low quality queue, right? I'm also sometimes too quick there, that's why multiple votes are required after all :7 – Tobias Kienzler Feb 16 '14 at 8:14
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    Yeah, I flagged it and realized "I'm way to tired to be doing this" and took a nap. Didn't last long though sadly... – Jon Feb 16 '14 at 8:15

What I also dislike is the fact that you don't get what you see in the editor.

The visual line break in the editor which is automatically set is not visible when reading the email in the sent folder. Also received flowed plain/text emails don't show the line breaks the author could see.

I fixed it by setting mailnews.display.disable_format_flowed_support to True while still composing emails as 72 width composed for mobile device compatibility.

Since I use a widescreen display (and I guess most of the Thunderbird users do) I'm not sure if it's a good approach to turn display flowed on by default. It's just ugly to have a 1 mile long line followed by a double line break followed by next very long line and so on.


Open a msg to type. At the top Edit> Rewrap. Fixed! Found this by exploring everything when it suddenly starting happening to me.

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