- exit thunderbird - locate prefs.js in profile - make a copy of it - edit it in a simple text editor, such as notepad - search for mail.warn_on_send_accel_key - change it from false to true - save and restart thunderbird

This can easily be enabled again from within Thunderbird.

• Menu icon > Settings > General
• Scroll to bottom and click on 'Config Editor' button

It will open in a new tab.

• In top search type: mail.warn
• Look for this line: mail.warn_on_send_accel_key

It will be showing a value: 'false' and the font will be bold indicating you changed this setting.

• On the far right there will be a toggle icon and next to it a left arched arrow - click on the arched arrow icon and it reverts to default.

So now the value will say: 'true' and the font will revert to normal non bold.

Thanks for answer. I checked both suggestions and unfortunately none of them worked :(

• Switching 'mail.warn_on_send_accel_key' true or false has no result on thunderbidr behavior. I'h also tried to restart each time I changed it.
• There were no entry 'mail.warn_on_send_accel_key' or any simillar in prefs.js file in c:\user\...\AppData\Roaming\Profiles\....

any idea what could be wrong?

re :There were no entry 'mail.warn_on_send_accel_key' or any simillar in prefs.js file

If : mail.warn_on_send_accel_key = 'True' This is the default so it's not going to get set up in 'prefs.js'. That is the setting you require.

If : mail.warn_on_send_accel_key = 'False' When you set to 'False', the font will become bold meaning it is a setting the user has chosen. Then it gets written to the 'prefs.js' file as follows:

• user_pref("mail.warn_on_send_accel_key", false);

As you were not getting the warning when using 'Ctrl+Enter', it sounded like you had a user preference set up as 'False'.

Hence why I advised you to revert back to 'True'. Please make sure that setting is reset to 'True' so font is no longer bold.

Note if you opened the 'prefs.js' file and altered the setting in thunderbird, then it will not immediately in the 'prefs.js' file because nothing gets written to a file that is already open. You would have to close the 'prefs.js' file and then reopen it using Notepad or a similar text editor program.

This should have worked, but can you check something. I'm just wondering whether some silly preference got created in another profile and it's somehow effecting how thunderbird behaves.

In this 'Profiles' folder C://Users/User name/Appdata/Thunderbird/Profiles Do you have more than one 'profile name' folder ?

If yes,

• Exit Thunderbird - it must not be running.
• Check the 'prefs.js' file in each 'profile name' folder.
• Open using eg: Notepad.
• Do you see a line saying: user_pref("mail.warn_on_send_accel_key", false);

If yes:

• Delete the line: user_pref("mail.warn_on_send_accel_key", false);
• Close up the empty space line, so it does not exist.
• Save the file.

check any other profile name folder for same.

Then start Thunderbird.

report on findings and results.

I did as you suggested and it seems that entering "mail.warn_on_send_accel_key" with value "true" or "false" using "prefs.js" or Thunderbird's built-in menu had no effect. Out of frustration I tried again but with all add-ons disabled and then it worked :) After additional research, it turned out that the "send later" add-on was to blame. I removed this addon and now everything is fine - changing "mail.warn_on_send_accel_key" now takes effect.

Fortunately, I no longer feel the need for this add-on, so the issue can be marked as resolved, however, it is still unclear why this happened.

Thanks for the help :)