A Mail User Agent (MUA) is the technical term from a email client application.
User agent in Mail User Agent (MUA) means that it's a user application (known as user agent on the web)
A MUA can:
echo -e "Subject:Hello World \n\n This is my first mail \n" | sendmail [email protected]
In the header field of an email, search for the value User-Agent
Example:
User-Agent: Heirloom mailx 12.5 7/5/10
The email internet address is composed of:
On Linux: