Ranked in these QuestionsQuestion Ranking
Pro Doubles as a to-do application
Mail Pilot turns emails into tasks. It has a built-in system of setting reminders and collecting emails into groups as to-dos.
Pro Good security features
There are options to display URLs you get in emails, or to disable pictures by default if you are afraid of getting malicious data from suspicious emails.
Con Makes a huge mess of IMAP mailboxes
Builds many new categories and basically uses IMAP as a database. Makes it difficult to work alongside other mail clients or webmail.
Con Not for everyone
Since it's mainly focused to turning emails to tasks and a strong believer of "inbox zero", it may not be suitable for everyone's workflows.