Thunderbird "unread email" counter doesn't always update when unread emails are opened

[Jesse]

BEHAVIOR
With Thunderbird in the Ubuntu Dock favorites, a counter will appear in the top-right showing the number of (I believe) a combination of unread emails and/or new email notifications. After opening some of those emails, the counter in the top-right doesn't always change. It looks like any unread emails that were present upon opening Thunderbird don't alter the counter when they're opened, but new emails received after Thunderbird is opened will alter the counter number when opened.

EXPECTED BEHAVIOR
For the counter number to be affected when emails are opened, regardless whether they were received after Thunderbird opened or not. (Could just be my ignorance as to whether the counter is alerting me of new email notifications or total unread emails.)

BUG DISCOVERED USING
Ubuntu 17.10
Thunderbird 52.4.0
GNOME 3.26.1
Nvidia 384.90 proprietary driver
X.org 1.19.5
Linux kernel 4.13.0-16-generic

[Sebastien Bacher (seb128)]

The issue is rather with thunderbird not sending updates correctly, it was doing the same sometime under unity

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[gazhay (gazhay)]

Still happening Thunderbird 60.7.0(64-bit) Ubuntu-GNOME 18.04.2 LTS

[[e-mail] (bcanderson)]

Still Happening Thunderbird 60.8.0(64-bit) Ubuntu 19.04