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have you tried the basics? Restart Thunderbird in troubleshoot mode and contunied when prompted to see if it gets fast in that mode?

Have you tried restarting your computer in safe mode with networking to see if some other program on your computer might be the issue? (wired internet connection required)

thank you Matt, for trying to help. As I said in my initial post,I have two gmail accounts that I access through Thunderbird. The fact that one of them works perfectly fine, and the other one doesn't, rules out these issues. The problem seems to be with the 400 or so emails that i keep in my "problem" gmail account. somehow the IMAP is causing this problem.

To narrow the problem, have you tried setting up a copy of TB with just the one gmail account? And recheck settings in Gmail itself. Are the two gmail accounts using the same SMTP server setting or are there two distinct ones? Puzzling, for sure.

Are the two gmail accounts using the same SMTP server setting or are there two distinct ones? Puzzling, for sure.

thanks, yes, same SMTP server settings.

That is, are they sharing one SMTP account in TB, or is there an SMTP server setting for each one separately?

David, thanks. Indeed it looks like they are sharing the same.

The fact that one of them works perfectly fine, and the other one doesn't, rules out these issues.

I disagree entirely. an empty account will work fine because it has no0thing to sync. Closed minds tend to not find issues because they are looking for a problem where the symptom is, rather than where the problem is.

The most common cause of slow sync and connection issues is anti virus programs. Unfortunately we have to try and lead people to that conclusion because they so frequently, like you have already, dismissed other involved applications in a quests to find something broken in Thunderbird.

Restarting Thunderbird in safe mode disabled certain graphics settings and most importantly disables customized menus and add-ons. Not just the add-ons you have installed, the ones that are injected into Thunderbird by external spam and scam filtering. The usual source being antivirus/ internet security suite that think they know what they are doing and should be allowed to inject their own code into running applications.

The second disables all the startup programs and thankfully get rid of the anti virus programs, VPNs and proxies completely so a real test can occur. Why do I fixate on this antivirus so much?

Antivirus programs inject code into running applications, lock files to scan them, just when the application wants them and perhaps most importantly scan every byte of information that comes down the wire into your computer, they routinely use man in the middle hacking techniques while advising people to be wary of such things. If the antivirus products do it well the performance loss for this is kept under 20%. If you have a very slow hard disk like the kind dell put in my cheap consumer device it was significantly more.

What most of them do relatively badly is actually test their products on desktop mail. They are rather careful not to interrupt Facebook or Netflix, but desktop mail is really only a niche market. A very small percentage of folks actually use a mail client to get mail, so gets little attention.

VPN' are another thing safe mode with networking stops loading. They have become quite fashionable of late, Mozilla are even into selling one, but few of them actually work with mail out of the box and some can not be convinced to work at all with mail. They are simply blocking all the mail ports and are designed for web browsing only.

You are looking for something that is making synchronization of an incredibly small gmail account excruciatingly slow, the problem to be blunt is unlikely to actually be Thunderbird. I do not dismiss it as possible, but it is not anything like the most likely cause. To put your problem account size into just a little perspective, I have a gmail account synchronized with gmail, it has over 200,000 emails in the all mail folder alone, and it is not slow. It is also running on a device with only windows defender on it.

Could you please do the following?

1. Open the menu > Help > More Troubleshooting Information, then click Copy text to Clipboard.
2. Go to https://pastebin.com, paste the info from your Troubleshooting Information page, use the Create New Paste button to create a page containing your info, then copy the resulting URL (address) of the page created.
3. Open a reply to this post, and paste the link to your troubleshooting information you just copied.

Or you could just copy it directly into the forum, but then you don't get to delete it later.

Hi Matt, No need to accuse me for being closed minded. You could have simply seen my comment as a question. I was trying to understand the logic behind your suggestion. I appreciate your detailed explanation and your efforts to help. Incidentally, before posting here, when I searched for an online solution, the first answer that came up was to start TB in safe mode, which I did, and didn't help.

As of this morning the syncing speed seems to have improved

Below is the troubleshooting info.

I assume TB comes in with several add-ons?

The only one that I installed was "Remove Duplicate Messages"

https://pastebin.com/ABw3dFvB

Hi Matt, No need to accuse me for being closed minded. You could have simply seen my comment as a question. I was trying to understand the logic behind your suggestion. I appreciate your detailed explanation and your efforts to help. Incidentally, before posting here, when I searched for an online solution, the first answer that came up was to start TB in safe mode, which I did, and didn't help.

As of this morning the syncing speed seems to have improved

Below is the troubleshooting info.

I assume TB comes in with several add-ons?

The only one that I installed was "Remove Duplicate Messages"

https://pastebin.com/ABw3dFvB