InboxPro has a good potential to be an excellent productivity tool for emails.

Good: The signature feature is easy to use, and the templates look good and professional.
Can be improved: Add custom text in the signature and allow to use of the custom link for the appointment feature instead of the built-in calendar.

Good: The email tracking works quite well and is not being flagged by spam engines like other tools I used.
Can be improved: The tracking has false positives. When you open the email, you sometimes get a "read" notification 1 second after sending.

Good: The email sequences can be very useful for sales activities
Can be improved: Add a custom follow-up email for individual emails to be sent automatically without starting the email as a sequence. Also, have the option to have a follow-up reminder for emails.