. after host name mail address

You're referring to the format of an email address!

After the hostname, the format of an email address typically includes the following:

• @ symbol (also known as the "at symbol")
• The domain name or top-level domain (TLD) of the email provider or organization

Here's an example of a complete email address:

[email protected]

In this example:

• john.doe is the local part or username
• @ is the symbol separating the local part from the domain
• example.com is the domain name or TLD of the email provider or organization

So, the breakdown is:

• john.doe (local part or username)
• @ (symbol)
• example.com (domain name or TLD)

This format is standardized by the Internet Engineering Task Force (IETF) and is widely used across the internet.