1. Easy E-mail Encryption.
2. More User Interface Options.
3. Mailing List Reports.
4. Allow users to see which spam checks failed.
5. Make top icons colorful.
6. Explain DMARC better in Mailing List interface.
7. Deploy additional themes beyond Dark/Light.
8. Bring back the preview pane.
9. Schedule your e-mail message to send later.
10. Compact view with 3X more e-mails on screen.
11. Show who's online in Interface to support chat.
12. Allow domain admins to view their connections/activity/spool live.
13. View all log data from a spool message.
14. Throttling based on domain being sent to.
15. Install SmarterMail on Linux.
16. Canned replies from webmail.
17. Include domain/user in IDS blocks view where applicable.
18. Double click IDS block to view summary.
19. Check all domains for MX record established and pointed to server.
20. Red Delete Button consistency throughout.
21. Show user who their domain administrator is.
22. Customize e-mail error code messages.
That is all I could think of for now. Thanks!