Thunderbird running slow with gmail

is you other account POP and the Gmail one IMAP perhaps?

My gmail is a POP account and the other one is an IMAP account.

So, no one here knows how Thunderbird and gmail work together, or don't work together well? That's really disappointing.

Slow is simply not normal, and might not have anything to do specifically with gmail.

Therefore, please spin through https://wiki.mozilla.org/Thunderbird:Testing:Memory_Usage_Problems

Unfortunately, this advice did not help. I have tried "compacting folders" and "repairing folders" and that does not help. I tried running Thunderbird in safe mode and no problems were detected. Performance was the same. I tried to start Windows 11 in Safe Mode, but instructions in Windows are awful and I was not able to get Windows into Safe Mode. The remaining instructions in https://wiki.mozilla.org/Thunderbird:Testing:Memory_Usage_Problems are very extensive and can easily take days and days. Unfortunately, I have a job and cannot spend days on a chase that might find something or might not.

As I mentioned earlier, my Thunderbird connected to my gmail is running slow. Thunderbird is NOT running slow on my other (non-gmail, Outlook) account. Does this not provide some clue as to what the problem might be? At this point, I would appreciate it if you could open a ticket on this problem. Thank you.

So, no one here knows how Thunderbird and gmail work together, or don't work together well? That's really disappointing.

I use gmail on POP for all of the email generated by this forum. It works well and reliably. You appear to be under some misapprehension that this forum is something other than a peer forum. Fellow Thunderbird users is whom you are addressing.

I do not have antivirus mail scanning as I have Defender looking after security and it is also working out well well after years I do not miss the regular mess that scanning made when accessing mail that most folk blame on the mail client.

Many Windows and now Mac users install third party antivirus products that scan email and in some cases they do it very slowly. It is always on my list of first suspects when trying to figure out why things are slow. (Windows safe mode should eliminate it, but few can use it these days because they almost exclusively appear to use WiFi internet connections and Windows does not load Wi Fi drivers in safe mode.

POP being what is is, downloads mail to a local store and that is the end of provider specifics. So running slow how I think is the obvious question. Downloading new mail (probably antivirus scanning is involved here) Accessing mail on the local drive (if you only have a single POP account with local copies then the antivirus may be slowing things, but if all mail is stored locally for all accounts and only one account is having issues accessing the mail then local disk failure and corruption could be an issue and needs to be considered. Run the Windows disk check tools supplied by Microsoft to determine the drive is healthy. The system will try to read a single bad sector many times before giving up so simple file access which your mail viewing involves can become quite slow. For windows I suggest or chkdsk Dell offers some detailed instructions https://www.dell.com/support/kbdoc/en-us/000148643/using-the-chkdsk-utility as do Microsoft. https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/chkdsk?tabs=hdd%2Cevent-viewer

Age is not a factor in disk failure. I have had them fail in hours or not until the motherboard caught fire after many years. It is indicative that the industry uses MTBF (mean time between failure) as the metric not "life of drive" so never discount to chance of random hardware failure.

Thunderbird is more prone to disk failure than many applications because it maintains what are, even today, quite large files (frequently gigabytes is size) this makes them slow for antivirus to scan (think in terms of 10 minutes per GB) and covering a relatively large swath or used disk space.

Compacting should normally create a complete new file for the folders mail storage (one folder one file + an index), but if for any reason the compact fails then that will not happen so it will remain on the dodgy bit that has been causing issues and may well have caused the compact to fail. We used to get feedback in terms of temp folders being left in the user interface when compacting fails, but code changes have largely eliminated the obvious signs of failure. So unless you are checking the error console (ctrl+Shift+J) you really will not know if a compact fails.

The next issue that affects Windows systems is temp folder clutter. Especially on systems that have more than a few months in service you can see the unmanaged orphans temp files in the folder becoming something that slows the operating system down and this can become quite apparent while waiting for temp files to be written sou you can view and email with a load of images in say. So clean up that mess as Windows does not even make an attempt. Again Microsoft offers instructions https://www.microsoft.com/en-us/windows/learning-center/how-to-delete-temporary-files

You asked if your situation provides a clue. Only in that is working well for others and not for you so it is something uniquely yours that is either causing or triggering the problem. All the testing suggestions revolve around this being a technically challenging area with many software intersections that could cause issues. Add to that the social factor that people do not like to be told their choice of antivirus or other software is the root cause. They usually want the symptom treated not the cause. So testing is designed to lead folk to the right result gently.

As for accessing windows safe mode. See https://learn.microsoft.com/en-us/answers/questions/5746991/how-do-i-start-my-computer-in-safe-mode

Which I will quote

Here are a few ways to boot into Safe Mode on Windows: Hold the Shift key while clicking Restart in the Start menu. This opens the recovery menu where you can access Safe Mode options. Open Settings → Update & Security → Recovery, then click Restart now under Advanced startup. From there, select Troubleshoot → Advanced options → Startup Settings → Restart. When the Startup Settings screen appears, press 4 for Safe Mode or 5 for Safe Mode with Networking. Press Windows + R, type msconfig, and hit Enter. Go to the Boot tab, check the Safe boot option, and restart your computer. Remember to uncheck this setting afterward to boot normally again.

One of those methods should work for you.