Which folder? What is the folder size on the server? WHo is your mail provider?

Provider: Google workspace Size: visible on screen ~45GB Folder: All (this is The name of folder)

I missed "gmail" in the account name.

In Thunderbird there should be a gmail folder named "All Mail".

In Thunderbird, on the account name in the folder list, right click and pick subscribe. In the subscribe menu deslect the "All Mail" folder.

Do you think this could be causing the slow sending of emails? Emails send very slowly, plus it always pops up a message that the message cannot be saved in sent.

I don't know whether it is causing slowness, and your assumption could be wrong.

But you should still unsubscribe that folder in Thunderbird, because it is not needed in Thunderbird. "All" is a special folder in gmail that points to messages from all other folders, including the Trash folder. That is why when you delete a message it still shows up in "All".

In Thunderbird, on the account name in the folder list, right click and pick subscribe. In the subscribe menu deslect the "All" folder.