The possibility to synchronize an account but not get notifications on new e-mails. (Probably related to #440, but I would want the account to still be synchronized). This could be useful for 'trash-accounts', which are used to sign up for various services. Usually, you don't need notifications for new email, but occasionally you still want access to them, e.g. for a verification link.
How would you like it to work?
Windows mail gives you that feature to toggle notifications
Relevant links, screenshots, etc