I see this myself periodically.

Does it help to set Max cache connections to 3 or 4, in server settings under account settings?

I've tried setting it to 4 and 3 in all my accounts, but unfortunately it doesn't seem to help

Does the error message give any more verbose info or reasoning/rationale? something like:

Max attempts reached

Any sort of configuration failure indicated?

Is Two Factor authentication enabled at all on ANY of those accounts?

   If so, any changes to settings or IPs ( if your 2FA/MFA is ip limiting?

No, it doesn't give any more information. Only the message of the Gmail server connection failure.

I can provide this crash report to Mozilla:

https://crash-stats.mozilla.com/report/index/bp-b7a20e83-dc23-41e7-95cb-360e60180917

It might be helpful for finding a solution to the problem.

Thank you guys!

If you are going to post crash information. Please post the information shown in troubleshooting information on the help menu. The crash id's link to the submitted crash report.

It appears you are having shutdown crashes, and that is not really related to your observed startup issues. Please try restarting Thunderbird with add-ons disabled from the help menu and see if that has any effect.

Ok, I've tried two things:

• First, I've deleted my Gmail account from Thunderbird, since it's the one that seemed to produce problems, but it hasn't had any effect.
• After that, I've tried restarting Thunderbird with add-ons disabled as suggested by Matt. Again and sadly, the problem persist.

Crah ids... are you going to post some?

This is a list of the crash ids I've submitted since Thunderbird isn't working for me:

• bp-c51988f9-7d79-43aa-81e8-835a00180919
• bp-d405cc59-bde8-4874-b641-bf8c50180919
• bp-9aad52f6-7469-4448-9b5a-6bc650180918
• bp-2442aca7-3104-4cd5-834c-31eb80180918
• bp-b7a20e83-dc23-41e7-95cb-360e60180917
• bp-33454a3f-7c58-4500-8257-9336c0180917
• bp-9a2c41cc-bab0-421b-875c-419a10180917
• bp-ce180836-8c64-4cbe-a63d-3ab4d0180916
• bp-2f969a0a-7d27-4df1-8806-b2abb0180916
• bp-350323d8-b9a6-4a94-8703-d73730180916
• bp-b2d1fe71-f1c1-4489-9ce4-1186b0180915
• bp-ac0eda52-27af-446a-bc14-1f2810180915
• bp-13b3b167-8f2b-4c69-8b18-f95400180915
• bp-b8dfda39-cf98-4afe-a8e8-e902f0180914
• bp-9b07bddd-5f3d-43c4-967f-a1f530180914
• bp-a518c20d-689b-437b-82cd-e03980180914
• bp-9963196f-9c30-4531-86c0-7b6760180914
• bp-a7be2e09-a61c-4613-96ff-142460180914
• bp-c4a48e55-ebcb-43b5-9068-4f9120180913

They're ordered from newer (19 Sep) to older (13 Sep).

Is this information useful?

Thank you very much for your effort!

PD: I've tried also by disabling an add-on called "Messaging menu and Unity launcher integration" and by removing a package that I recently installed in Ubuntu called "thunderbird-gnome-support". However, none of these solutions worked.

I can see where this same issue has been raised as a bug on Debian for multiple programs. I can see it raised as a bug for Firefox 63

But a cause or solutions I do not see.

Just to play a hunch, go here and make sure the setting is turned on.

I went to the page and I had the setting turned off, but unfortunately, after turning it on, the problem persist. Anyway, thank you for your answer.

I've tried also by deleting all my accounts in Thunderbird and I'm now trying to set them back, but I can't, since the "Mail account setup" window doesn't let me click the "Done" button after saying password is ok. Weird, isn't it?

I'm noticing now too that the crash doesn't appear after closing Thunderbird. It may be a little improvement over the previous situation.

Thank you one more time for your help!

I've finally found a solution for my problem. I deleted all the content into the Thunderbird information folder. I found it in the "Help" menu -> "Troubleshooting information" -> "Open directory".

It allowed me to reconfigure all my accounts and now Thunderbird is working well again.

Thank you all for your help!