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1. The ability to create anonymous email addresses, which work pretty much like an alias, except that it is associated to a single user, it is permanent (until deleted by the user), and a user would be able to send an email from this address (unlike an alias). Use case: think of when you need to provide your email address to some commercial website. You know they will leak it sooner or later, you know they will spam you sooner rather than later. Give them a dedicated email address and when either happen you can delete this anonymous email and no more spam or account that can be correlated to another website when they get hacked.
2. The option to make STARTTLS mandatory on SMTP and IMAP and deny unencrypted connections (99% of which is spam). Perhaps also showing statistics of incoming traffic by encrypted/unencrypted.
3. On My Today Page, show the list the 10 previous connections with IP, country of IP and device used. This is a security measure to give the user an opportunity to spot an illegal access to his mailbox.
4. For certain "super-user", it would be useful to have the ability next to "Block sender" to also block the incoming smtp server. Blacklisting smtp servers is a more definitive way to fight spam. Of course this would require an explicit delegation.
5. Silent auto-update, google chrome style. I would love to have the option not to have to update smartermail manually and for the program to have the ability to self update itself (subject to the current license still allowing the upgrade).
6. Move the logout button directly next to Help at the top right, instead of in the drop down. I would like to be able to log in and out quickly, this would save a click every time.
7. Why can't smartermail use the SSL certificates from the Windows/IIS certificate store (for IMAP/SMTP)? The current approach requires keeping unencrypted certificates in the smartermail folder which is not ideal.
...because I still believe in Santa Claus!