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Thunderbird is extremely slow after the new UI update 115.4.2

Making moves

I've got this big new update with new UI that simply doesn't work.

I do lot of operations over IMAP and the UI rendering is so extremely slow, that I'm unable to work with my mailboxes. Steps to reproduce, using IMAP, with config to mark as deleted and manual purge:

* Select 500 unread email messages.

* Delete them

* Purge the mailbox

It either takes very long, while rendering each message change back and fort, or completely freezes.

How do I downgrade and block further autoupdates?


Making moves

As a fanatic Thunderbird user for many years -for that reasson made a free dontation- I am very disapointed and have the exactly same problem. Please solve this. Otherwise, I like to downgrade soon as possible..... as it is unworkable at this moment. My mails are my business life line.

Making moves

I have the same problem. Changing the user interface does not bring any advantage, it forces you to start a new learning curve (adaptation). If it also creates stability problems, it means that time has been wasted on the superfluous instead of improving the productive. Anyway, thank you for making this wonderful working tool available to people.

Making moves

Same slowness when deleting similiar amount of messages, using POP here, so this is just UI i guess.

Making moves

SAME!!! driving me NUTS on all 8 of my different machines i use!! super slow!! hate it!

Making moves


Making moves

Thunderbird on Ubuntu 20.04 LTS. Extremely slow after upgrade to 115 (currently 115.05.0 (64bit). I am using Thunderbird for over 15 years and it was never bad like now. Really fed up now., it has been lagging since some time in September. Multiple sequential upgrades never fixed anything. Thinking to switch over to something else or downgrade. It seems that mozilla team shows more and more ignorance to public

Making moves

I ended up downgrading, and losing all my settings in the process. Version 102.15.1 seems to be usable.

I went to, copied the link from Download button and replaced the version. 


I am also running 115.5.0 (64 bit) on Ubuntu 18.04.6 LTS  and it runs a way much faster, basically acceptable. The same accounts, same settings. In fact it includes much more historical data on disk, which does not affect performance at all.

Making moves

One account works fine and the other one is so slow I age a year every time I try to delete a message.

Making moves

Exactly same problem with Thunderbird in Supernova version (expecially in latest release), slowliness everywere.....and not in selecting and deleting or moving tons of email, but simply openig emails just received...

I'm a Thunderbird user since first release and every time I can I try to recommend it as "the best mail client", but with those slowness problems I only risk making a look bad.......I'm very disappointed

Making moves

Like so many others I find the current version (115.5.2) SO SLOW. Simple deleting just ONE email can take at least 10 seconds and as the screen doesn't change you cant be sure that the <delete> command has registered. It is VERY frustrating to say the least.

Making moves

I appear to have an auto-update that went in yesterday without me noticing.. now 115.5.0 64 bit on Ubuntu 22.04. TB just ground to a halt. I don't know what is happening but this has just become unusable. If it is re-indexing then it is re-indexing the _world_.

Making moves

Thunderbird freezes.

I need to install last year's version and cancel updates.

Making moves

So time to cut to the chase.
(the following are descriptions of context, showing the latency)
1. Left-click on a folder in the left pane; right-click to show secondary floater menu; select "mark folder read": 5 seconds
2. Left click on left pane/folder expand/contract arrow: 5 - 10 secs (varies)
3. Left click on left pane (waiting for right-hand pane to show folder contents: 5 seconds
4. (when viewing right-hand pane: folder contents: 600 messages in the folder) using slidebar to track up  and down the folder, so going from "right at the bottom" to "right at the top": 5 seconds
5. Left-click on a folder in the left pane; right-click to show secondary floater menu; select "create new folder": 8 seconds
6. Click on search bar, enter text (type-ahead): 8 seconds for text to appear and search to start
7. Right-click on trash in the left pane (to select "empty trash" (17 messages)): 10 seconds to display 
8. On closing always get the pop-up saying "unresponsive window, do you want to close" - but then always eventually gets there and closes.

"5 seconds" appears to be a regular occurrence. Issue with servicing the key-press and mouse click queue?

In other respects this wonderful new interface is an unmitigated disaster and whoever decided that it was ok to release TB115 in this state should be SHOT !!! 

Making moves

(and to add insult to injury:)
9. click "help" tab / "about": 9 seconds to display the pop-up ... 

Making moves

So whats your plan, then?


Not sure they have one. Do they even bother to read these comments?

They need kicking.... I'll kick them.

Making moves

I'm on Thunderbird 115.6.0 (64-bit) / Windows 11.

Doing my New Year's mailbox clean-up, I also noticed that bulk deleting or archiving mails takes a lot of time, making the whole experience rather sluggish.

The process was a lot slower on my Google account than on my Hotmail account, however.
I hope the developers can look into this and speed up bulk processes.

EDIT: Thunderbird froze multiple times during the process 😞

Making moves


Making moves

Message from Wayne Merry:

  • Moderator
  • Top 10 Contributor
1/3/24, 12:18 PM
more options

Glad you have arrived here for support. Please have a look at the details in the items at Which ones, if any, match your issue?

p.s. the discussion area at Connect is just that, not a support venue. The discussion posting page at
boldly recommends "If you need help with a technical or performance issue, visit Mozilla Support."

Making moves

But the problem now seems fixed... don't know what he did mind.. hacky magic !!
Version is now 115.5.0. Guess it did an overnight update....

Making moves

Thunderbird 115.6.1 is unusable. E.g. when trying to reply to a message, my laptop with 32 GB of memory and Ryzen 7840HS CPU lags so much that you have to wait like 2 seconds after each key press. It's impossible to write any emails with this app.

I do not agree, with an old Intel Core i5-2500K and 16 GB of memory I noticed a preformance improvement in latest release restoring a quite normal behavoiur even on this outdate hardware configuration. Lags are not completely eliminated, but In my opinion, the improvement is evident.

Well obviously Thunderbird settings have something to do with the problem. 

For example when I disabled the setting "Enable global search and indexer". I also disabled "Allow Windows Search to Search Messages".

It's now a lot better. But it DID lag massively with those settings on. My email accounts use IMAP so that's another angle to investigate (does the new Thunderbird run worse if accounts use IMAP vs POP3?).

I have those settings enabled by default, I'll try disabling to check for best performance....

Making moves

I use Windows 11, and the mailbox data is placed on the NAS, because I have different computers that need to use Thunderbird. I use version 115, and it becomes very slow when using it. Whether it is receiving, deleting, or moving mails, it is very slow. I changed it back to version 102.15.1 and it became normal.

Making moves

Yes, same for me. Very slow. Even sending emails take time. Which is very frustrating.

Making moves

I can't understand what's going on. There are a zillion complaints all over the place about this issue, and I see nothing (anywhere) from TB about a solution or workaround. 

What makes this more frustrating... suddenly... and regularly... the slowness completely disappears. But I have no idea why.  It has a brain all of it's own. 

Has the slowness issue of 115.9.0 been resolved? Because I have been afraid to update, I am still using 102.15.1

No, it hasn't. It is still very slow.

Making moves

Same problem here with drag & drop. Moving emails from inbox to a folder (IMAP) takes insanely long, like ~15 seconds for 5 emails. I'm thinking about moving away from Thunderbird for good (after having donated a couple of months ago 😠). V. 115.10.1 (64-Bit)

What do you have in mind Matt? I also want to move away from Thunderbird. 

I looked around yesterday, but there isn't much choice that appears better. Thunderbird has the cross-platform advantage, but apart from that, MS Outlook isn't bad and performance is definitely better. Everything else I found did not really convince me. 😑

Thank you Matt! I shifted from MS Outlook to Thunderbird as Outlook was not able to handle lot of emails. So, I guess I need to stick to Thunderbird.

Making moves

I am also having this problem on my Windows 10 computer since December or early January. Interestingly, it has NOT occurred on a Windows 7 computer I frequently use. Both machines are running the 32-bit version. I notice it most when going through emails in my inbox, which I do daily. I typically keep about 15 emails in my inbox that are action items for the near future (most of which are starred so I can sort them to the bottom of the list). With only this many emails in the Inbox, speeds are almost normal, but once it exceeds this, I start to get several second delays in loading (not downloading, but waiting for the message to display in the preview pane - I almost never actually open emails), and in displaying the next message after dragging a message out of the inbox to another folder. The header from the email I just moved lingers over an empty message box for several seconds before the message I have selected in the message list displays.

I have also noticed occasional improvements, usually after I have signed out of Windows and signed back in, or rebooted completely, but after awhile, the problem always comes back, which makes me wonder if there is some kind of caching issue and the cache is becoming full, and not emptying automatically as intended. I suspect there may be some kind of underlying Windows issue, as I am experiencing something similar in another program.

Since Mozilla apparently ignores this forum, perhaps other participants with a deeper knowledge of Windows can speculate on what might cause this kind of issue?