What is "mail", and how is it navigated?

This page describes the interactive command in detail, and is in fact a fairly thorough tutorial. Describes commands such as z and z- :

If there is more than a screenful of messages, then z will
show the next screenful, and z- will show the previous screenful.

mail isn't Pine; it's just mail. In a perfect world, your version of mail should be compatible with POSIX/SUS's mailx program (The most relevant documentation being under the "Extended Description" heading), but, as usual, determining the deviations from perfection is left as an exercise to the reader.

As its manual states, mail is:

mail is an intelligent mail processing system which has a command syntax reminiscent of ed(1) with lines replaced by messages.

That is to say, you could think of it as a quick way to perform some tasks related to the mails you receive in the server you are working on.

The power of mail can be understood when writing shell scripts or cron jobs for example.

To learn it better, I've found some articles about mail command:

• Mail Command to send and receive mail.
• Shell Scripting with mail Command.

Another question made on this site deals with the same issue:

• using the mail command.