After installing 12.2 (x64) on my work-computer I’m experiencing awful performance with Thunderbird. Switching between folders can take several seconds. I used to run 12.1 on this machine and did not experience anything like this. When switching between folders an busy mouse pointer appears, once the folder is loaded everything is quite snappy. I’m pretty sure this is a local issue. The connection between my computer and the mail-server is more than 100Mbit.
To create a reference I also installed kmail and there is a massive difference where listing a folder with several thousand mail is done without any delay.
I have a ‘feeling’ when loading the mailfolders in Thunderbird xorg and Thunderbird consumes to much CPU, what strikes me as odd is that if setting Thunderbird to offline mode it’s as snappy as expected.
I’ve found a few post on the net stating there have in the past been similar issues with GTK apps in KDE.
Several thousand mails is the key here I think. I use KMail and it is really fast, but the reason for this is that it downloads all mail on my computer for offline use. So when switching folders in KMail, no network access is required. Actually I think that only the headers are stored, but anyway.
Now, I used Thunderbird only for a little bit and a really long time ago too, but it sounds to me that every time you click on a folder, Thunderbird refreshes it’s contents, and if you have a few thousand mails in each folder, well, it certainly takes time…
Anyway, perhaps there is a setting in Thunderbird, that enables it to store mail on your machine (or the headers as with KMail), and another one that will stop Thunderbird from refreshing on every click you make on a folder.
If an email account is set up as a POP account the folder’s contents are downloaded from the mailserver one time and stored on the local disk. Subsequent viewings only require access to the local disk. That’s very fast.
However, if the account is set up as an IMAP account all the content remains on the mailserver and must be referenced from there every time it’s viewed. I use IMAP accounts to synchronize folders across multiple PCs. The drawback can be that it takes along time to refresh a folder containing a large number of messages. The easy solution is to create archive folders (very easy in Thunderbird) that are local and move older messages to those folders. By keeping only current content in the IMAP folders the refresh that takes place every time you open the folder is very fast.