When comparing sup vs Alpine, the Slant community recommends Alpine for most people. In the question“What are the best command-line email clients for Linux?” Alpine is ranked 2nd while sup is ranked 7th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Extendable
Sup's features can be extended through extensions developed by the community.
Pro Supports a large number of emails
Sup describes itself as "a console-based email client for people with a lot of email" and rightly so. The hierarchical interface that sup provides and support for tags allows users to easily manage and navigate a large number of emails.
Pro Extremely user-friendly
Pro Can use the built-in text editor or can be integrated with another text editor
Alpine comes with pico, a lightweight text editor which can also be used as a standalone tool. It can also be integrated with vi, vim, emacs, etc... if the user prefers to do so.
Pro On-screen contextual help
Alpine has contextual help that can be displayed on-screen. Removing the need to consult the man pages every time you forget a command or how to do something inside it.
Cons
Con Updates are not frequent
Alpine is not updated frequently. This means that new features, bug fixes or security updates come much later than in other email clients.