Unable to connect to imap server. (Linux)

[pete of ebor]

Hi. I've been using TB for many years, but I have recently begun to receive this error when starting TB. It does not appear every time, but through trial & error, I think I've narrowed it down to it appearing every time TB is first run after a shutdown. I have five email accounts [all imap] but this error only ever refers to my gmail account. Closing TB and re-opening usually [but not always] fixes the issue. Once fixed, TB works perfectly..

"Thunderbird
Unable to connect to your imap server. You may have exceeded the maximum number of connections to this server. If so, use the Advanced IMAP server settings dialogue to reduce the number of cached connections."

I'm running TB 102.4.2 on Linux Mint 20.3 Cinnamon
Any ideas ?

[Grumpus]

Open settings from the three bar icon.
Go to General Tab/Advanced and open config editor (bottom of page)
Type connections into the search block Runs across the top of the page and see what the counts are for specific items.
network.http.max-persistent-connections-per-server
network.http.max-urgent-start-excessive-connections-per-host
may be the ones to alter (up the ante) but look at the other ones in the list, particularly the "keep alive" items.