One thing was still wrong in my perfect Thunderbird/GMail setup: the Trash folder. The default location of the trash folder in Thunberbird is not the same as GMail’s. So, if you want things to work seamlessly, you also need to remap that one. For this one, there are no user-friendly settings you can tweak though. You need a bit of hardcore config editing:
- Go to Tools > Options and click on Config Editor on the General tab.
- Find a key of the form mail.server.serverN.hostname with the value imap.gmail.com.
- Create a new key mail.server.serverN.trash_folder_name and give it the value
[Google Mail]/Deleted Items.
- Restart Thunderbird
update 12 January 2008: Apparently, Google has changed the name of the trash folder from Deleted Items to Bin …