Meaning of the word "regular mail" in English

What does "regular mail" mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

regular mail

US /ˈrɛɡjələr meɪl/
UK /ˈrɛɡjʊlə meɪl/

Noun

the standard postal service for sending letters and packages, as opposed to electronic mail or courier services

Example:
I sent the documents by regular mail, so they should arrive in a few days.
For urgent matters, it's better to use email instead of regular mail.