I think that should be checked without opening every session. With much directory, open every dir is very noise, if new mails arrive and are filtered into sub-folder, i can't see them. Can you fill a bug report?
This is actually by design. The operation that checks whether new messages have arrived can be quite costly for the IMAP server and therefore for the SOGo process that is in use for the operation. In order to reduce the load, we limit this to the folder that have been opened because we consider that those are the ones that the user really use. Chances are that a lot of users have a lot of folders that are of very little interest to them so it we be useless to check them too every 2 minutes or so...
Cheers, -- users@sogo.nu https://inverse.ca/sogo/lists
