User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Firefox/78.0

Steps to reproduce:

On Ubuntu 16.04 was updated from 68 to 78 using software updater, after update I am no longer able to open emails in tabs

Actual results:

Emails will not open in tabs, only in a new window

Expected results:

Emails should open in tabs

(In reply to Kim from comment #0)

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Firefox/78.0

Steps to reproduce:

On Ubuntu 16.04 was updated from 68 to 78 using software updater, after update I am no longer able to open emails in tabs

Actual results:

Emails will not open in tabs, only in a new window

Expected results:

Emails should open in tabs

Seriously?

Ubuntu is usually very late in updating Thunderbird. The last one I received was 68.10.0 from 68.8.0.

I'll have to wait for the update from Ubuntu.

I have no problem with 78.0 installed from Thunderbird on 18.04.4 LTS.

Do you have the same problem using Help > Restart with Add-ons Disabled?

Yes Seriously.

OK, have tried the suggested Help > Restart with Add-ons Disabled and emails are now opening in tabs.

However, I have also tried systematically disabling the Add-ons one by one (not that there are many: FileLink Provider for Dropbox, Get All Mail Button Thunderbird, and Provider for Google Calendar) but that doesn't make any difference.

There is one additional step within safe mode that work for someone at https://support.mozilla.org/en-US/questions/1295225
Does that help?

YES! That works, thanks

wfm per reporter's comment 4