Do you still experience this if you close and restart Thunderbird in safe mode?

Hi, this does not change anything. I even reinstalled thunderbird without being able to recover this function.

Just in case you are not aware, a single click will open the message in the lower Message Pane.

Confirm settings in Options: 'Tools' > 'Options' > 'Display' > 'Advanced' tab or 'Menu icon' > ' Options' > 'Options' > 'Display' > 'Advanced' tab Open messages in:

What have you got selected? 'A new Tab' or 'A new message window' or 'an existing message window' ? click on OK

I have already tried to modify these options, whatever I choose, my double click does not open a new window. Of course, a single click opens the message in the lower message pane but I prefere not to use this space for practical reasons. Thank you

re: Of course, a single click opens the message in the lower message pane That's good to hear, so at least you have access to read emails.

re :whatever I choose, my double click does not open a new window. If you want it to open in a new window then you have to choose that option. Choosing another option will not offer the same result, but I can understand you have tried to get the double click to work on anything.

At this point please make sure the correct option is selected.

Can you try this: Make hidden files and folders visible.

• http://kb.mozillazine.org/Show_hidden_files_and_folders

In Thunderbird

• Help > TRoubleshooting Information
• click on 'show folders' button

a new window opens showing contents of profile folder name.

• close Thunderbird now - this is important

Look for and delete the following files:

• panacea.dat
• session.json
• xulstore.json

Close folder Restart Thunderbird.

Report back on results.

I deleted the indicated files but the problem still the same

Please confirm settings in preferences.

'Tools' > 'Options' > 'Advanced' > 'General' tab click on 'Config Editor' button - it will tell you to be careful :)

In search type: openmessage

To open in 'new window' you should have these settings: mail.openMessageBehavior; Value = 0 mail.openMessageBehavior.version; Value = 1

Do you have these settings?

If no: double click on the mail.openMessageBehavior line a small window opens allowing you to enter a 0 (zero) and then click on OK.

Click on OK

Restart Thunderbird.

Hello and many thanks for the effort to help! Indeed, my settings looked different, I have "2" for mail.openMessageBehaviour and 1 for the .version. However, when I switched from 2 to 0 and restarted Thunderbird nothing changed.

The mail.openMessageBehaviour option should be: 0 = new message window 1 = existing open window 2 = new tab

Please see if something is overriding the preference you have set now that you have set the preference in config editor. In thunderbird 'Help' > 'Restart with add-ons disabled'

Great, I had to erase the complementary modules and everything works now perfectly. Many thanks and best regards Oussama