Thunderbird Inserting Unnecessary Line Breaks

Discussion of bugs in Mozilla Thunderbird
Posts: 2
Joined: October 6th, 2020, 11:46 am

Post Posted October 6th, 2020, 12:17 pm

After an extraordinary amount of testing, I can conclude that Thunderbird is placing linebreaks inappropriately in emails sent from Thunderbird.

In other forum posts, I saw these described as "soft" line breaks that email clients could ignore, but in my testing, Gmail, Yahoo, Outlook/Office 365 all display these false line breaks (in both webmail and mobile apps). In fact, the only email clients that did not display these false line breaks were Outlook 2016 (Windows 10) and Thunderbird (Windows/macOS).

The issue is that Thunderbird is inserting these line breaks where the line changes in the view of the composer. This is an arbitrary line that really serves no obvious purpose, given the thousands of possible variations in screen sizes on mobile or desktop?

Toggling between sending in HTML or plain text seems to not have an impact in resolving this issue, and neither does switching between "Paragraph" or "Body Text" modes.

Any hope for a resolution on this issue? (via Extension or correction by the developers?) Or any other suggestions on where I should post this?
Last edited by williama6 on October 6th, 2020, 1:09 pm, edited 1 time in total.

Posts: 2
Joined: October 6th, 2020, 11:46 am

Post Posted October 6th, 2020, 1:08 pm

For posterity for others looking to solve this same problem, another forum poster suggested this solution (, which appears to fully solve the problem:

Set mailnews.wraplength to 0 (zero) in Options/General/Config. editor to wrap plain text messages to the window width

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