Most of the time you do not need to worry about the protocols as the Mail Client application (once set up correctly) deals with this.
However, if you use some old and fairly primitive mail clients you might be able to see the protocols in action or even have to converse in the PROTOCOL yourself.
If you use the UNIX mailx mail client for example this fairly primitive mail program provides a text command line based interace where you almost talk at the this level.
If you need to resort to writing mail client applications then you will need to write or converse with the mail server in the PROTOCOL. This is not difficult to do especially when using high level Mail and even FTP protocols.
For now let us just see what the protocol looks like and how it might actually be used in practice. We will study SMTP and POP which a simple protocols that repsectively send and retrieve email.