User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:86.0) Gecko/20100101 Firefox/86.0

Steps to reproduce:

I am a long time user of TB, I think more than 20yrs now and I never thought to switch to another mail cliend even as I have an Office 365 home subscription with Outlook. So I am still continueing to use TB, but since a few years it is annoying because of performance of TB user interface. It gets worse with every new update, specially in the last monthes I see more and more performance issues.

I have set up several mail accounts in TB and my mailarchive is about 20-30GB in size, even keeping very old emails if they are still interesting/important. I have filters to sort incomming mails in douzens of folders, so call me a TB power user.

I am using TB on mainly two systems, one is a small laptop using an 7 years old Atom based Pentium CPU, the other is a highend Xeon workstations with 8 cores, hyperthreading, 64gb RAM, and both are using big and fast SSD where also the mailarchive is stored. I have not installed any addon in TB.

Actual results:

TB is very slow in user interface. It does compressing folders while checking for new emails. It does compressing folders while using TB actively. It checks several email accounts at the same time and complaining that automatic filters can not work because folder is in use. TB is very busy with itself while I want to use it, it does not react to on mouse clicks, not on the small laptop, and not on the Xeon workstation.

If I try to answer an email while it does all these background tasks, it is very often impossible to write into the message, the characters only displayed after seconds to minutes, etc. While answering a mail, the main window appears in the front of the mail window and no reaction to switch back to the message window, and a lot of such annoying things. Manually moving mails to another folder is also complaining often while backround activities like compression or mailchecking are running.

Some times TB is like unuseable. In Windows taskmanager I observe that there is only one process, while Firefox uses several processes/processor cores which could spread over 4 to 16 cores on my computers.

Expected results:

Impprove performance massively, by using multithreading, make backround tasks like folder compression in the backround while TB is idle. Stop backround tasks like compressing while email checking, while user interaction. Avoid compression of folders which have not been touched since last compression. Make TB more performant, make it more useable again.

(In reply to Stefan Matthäus from comment #0)

... Manually moving mails to another folder is also complaining often while backround activities like compression or mailchecking are running.

What is the exact wording of these alerts? Is it perhaps one of these?

• Bug 288896 - eliminate modal dialog window, move to activity manager entry, to avoid frequent interruptions by popup saying "Cannot move messages to folder <name> because another operation is in progress" [pop3]
• Bug 837620 - Folder Compact on Thunderbird startup, or switching to newsgroup, results in error "Operation is in progress"

How many pop accounts and how many imap accounts do you have?

Pop: 5, Imap: 1. Bug 288896 fits well, sometimes I have to click that message box a douzen of times until all mails are downloaded, and then run the filter manually. But for folder compression and general performance while email syncronisation I do not have "Operation is in progress" message. Just slow motion while browsing through the email folders, scrolling/reading and answering emails. It's also not only while startup, often for example compressing just starts when I switch back to TB window after hours of idle. In sich cases sometimes it is faster to work with TB when closing/restart TB. Maybe it helps you to know that I have about 80-90 mailfilter rules to sort mails in folders, by sender adress, by keyword, etc.

(In reply to Stefan Matthäus from comment #2)

Pop: 5, Imap: 1. Bug 288896 fits well, a) sometimes I have to click that message box a douzen of times until all mails are downloaded, and then b) run the filter manually.

I've never encountered anyone who had to do "a)". So you clicked "proceed" and been prompted multiple times? Does it matter how many messages are being downloaded?

A couple years ago for an imap inbox account I did need to sometimes run filters manually after downloads. That problem is long gone for me.

But for folder compression and general performance while email syncronisation I do not have "Operation is in progress" message. Just slow motion while browsing through the email folders, scrolling/reading and answering emails. It's also not only while startup, often for example compressing just starts when I switch back to TB window after hours of idle. In sich cases sometimes it is faster to work with TB when closing/restart TB.

Not a surprise that startup is not the only time you see problems.

How many messages in your largest imap and largest pop Inboxes?
And in the imap trash folder?

Do you use the pop option "keep messages on server"?
How much memory is Thunderbird using when you need to restart it?

Do you ever see unresponsive script? Bug 929281 - Long startup and "Unresponsive Script" with many pop accounts and check for e-mails on startup. View > Folders > All, with version 18/version 24

Maybe it helps you to know that I have about 80-90 mailfilter rules to sort mails in folders, by sender address, by keyword, etc.

That is helpful. I do feel that version 78 is a little slower in this area. FWIW I have 150 filters for one of my imap accounts

questions in comment 3

Also, which antivirus software do you run?

Just Defender, no other.

(In reply to Stefan Matthäus from comment #5)

Just Defender, no other.

there were several other questions in comment 3 ;)

Answer:

Do you use the pop option "keep messages on server"?

• For pop email account I have set on both computers to delete emails from the server after 4 weeks. Additionally the laptop is setup to recieve emails only if they are younger than 1 week. So I keep laptop and workstation syncronous. So pop email server size is always quite small.
• Googlemail is by imap and deleting messages there has no effect, they remain.
• I don't use trash folder on imap

How much memory is Thunderbird using when you need to restart it?

• Thunderbird uses at least 500 MB RAM in idle on my Xeon, 150 MB on my laptop, for busy I have to check. But I don't expect that it is using 64 GB to block my XEON workstation...

I don't think the prorlem is about pop/imap mail amount, it is because of TB does folder compression while download email. There is no multitasking and no intelligence in this compressing task.

Some times TB is like unuseable. In Windows taskmanager I observe that there is only one process, while Firefox uses several processes/processor cores which could spread over 4 to 16 cores on my computers.

I'm sure version 91, out in a few weeks, will be better. Until then...

Are you using any message filters on message body?
How many messages are in the gmail "All Mail" folder"? And have you unsubscribed from that folder in Thunderbird?

Just Defender, no other.

Is defender set to exclude the Thunderbird profile directory?

For pop email account I have set on both computers to delete emails from the server after 4 weeks.

Where exactly do you have the retention policy set?

I don't use trash folder on imap

Please explain what this means - because every imap account has a trash folder. Are you using Mark as Delete preference?

I don't recall ever having TB hang as described. However, I DO have issues in Firefox 89 & 90 (public release versions) where the cursor hangs and/or the screen freezes for many seconds, pretty much as described here but not for so long.

I found this was due to the BITDEFENDER Anti-Tracking extension (currently 1.3.0.15). Is this the AV program referred to as "Defender"? When I turn off this extension, all works well and performance is smooth & clean. With it active, the mouse hangs or screen actually freezes for many seconds every time a page loads -- and every time something significant is activated on that page (such as a mouse-over). Happens even as I interact and write on THIS page!

FYI, I'm running Windows 7/32 Pro (in Aero mode) on Dell Precision and Latitude PCs, always with the latest TB, FF, and respective anti-virus updates.

I have reported this issue to BITDEFENDER tech support, but they insist it is due to some co-existing DELL AV piece which has been present since this machine was new back in 2010. I don't have the issue on my non-BD machine with the same DELL piece. (I thought I reported this to Bugzilla too but can't find a record of it.)

Stefan, sorry for the delay in following up. It would be helpful to know your results with the following

it is because of TB does folder compression while download email.

1. Automatic folder compact can be turned off. (if you still on version 78) Tools > Options > scroll down to "Network and Disk Space" > uncheck "Compact all Folders". What value is in the field "save over ____ MB total". Thereafter, you'll periodically want to do File > Compact Folders.

Is defender set to exclude the Thunderbird profile directory?

2. The following describes Defender causing performance issues and describes how it is easy to avoid https://www.startnet.co.uk/how-to-exclude-mozilla-thunderbird-from-windows-10-defender-anti-virus-when-thunderbird-is-running-slow/

Stefan, something I had forgotten to consider. You said you have mostly pop accounts, but one imap account, and "I don't use trash folder on imap."

This likely means you are seeing Bug 218075 - Compact of IMAP folder with many deleted message slow with IMAP delete model (Mark as Deleted) because of expunge notification from the server for every deletion

Does that sound correct? If so, then the problem is largely imap related.

Does that sound correct? If so, then the problem is largely imap related.

I deleted about 17k large messages on a fully sync'd imap folder with "just mark as deleted" (aka, imap delete model). Then compacted the folder to expunge them. The expunge imap command did result in 17k "* xxxx EXPUNGE" lines but that took about a second on the wire. After than tb immediately asked for quota data and the flags on each message, and that was instant on the wire since there were now no messages. Then there was about a 25 second delay were the UI was frozen before the next imap command was sent to IDLE the connection.

But doing the same experiment and deleting and expunging only 20 of the 17k messages, resulted on no noticeable UI freeze. I think this would be more typical of normal usage.

Maybe the reporter could disable compacting temporarily and see if that is really causing the slow downs. It's under General Settings / Disk Space. Then restart tb to make sure the change takes effect.

Stefan seems to be gone. But we'd gladly take more information.