Mailboxes and mail addresses

Mailbox vs. email address

It would probably surprise few people to learn that the email addresses accounting@idiom.com and support@idiom.com, deliver mail to more than one person's mailbox and that some people's mailboxes can be reached by more than one of these addresses.

The point is that "mailbox" and "email address" are different concepts. Email addresses are used by people sending mail, mailboxes are used (as POP usernames) by people receiving mail.

One email address can reach multiple mailboxes

One mailbox can be reached by multiple email addresses

How to use a mailbox

Two kinds of "login"

To use a mailbox, there are two stages of login that must be done in sequence. When people have only one mailbox, we can make things simple and shield them from this complexity. However, when you have a second mailbox the second login stage specifies which mailbox you access, so you need to know about these logins.

The two stages are:

• attach your computer to the network (network login)
• access the mail server (mail login)

Attaching to the network is a necessary first step for anything else you do. In this stage, your networking software tells our network who you are by sending your login username. It then sends your password to prove that you are authorized to log in with that username.

Once connected to the network, you have access to the services on the Internet, including your mail. To log into the mail server, your mail software sends your mailbox name as your mail username, along with your mailbox password.

The network login uses a language called "PPP", which stands for Point to Point Protocol. The mail login uses a language called "POP", for Post Office Protocol. The mail username is typically called a POP username, or POP3 username (to indicate that the third version of POP is being used.)

For accounts using only one mailbox, the network login and POP usernames are the same. The network login and mailbox passwords are usually the same too.

Accessing Extra Mailboxes

When there are multiple mailboxes for an account, the network login is the same regardless of which mailbox is to be accessed. All users of the account log into the network with the account username and password. They can then access different mailboxes by logging into the mail server using the different mailbox names as the POP usernames.

The name of the primary mailbox is always the same as the network login name.

For example, suppose John and Kathy Smith share an account named jsmith. By default they have a mailbox with the same name, and the email address jsmith@idiom.com delivers mail to that mailbox.

They can also have a mailbox named, say, ksmith, and the email address ksmith@idiom.com will deliver mail to that mailbox. Then they have one mailbox for John and one for Kathy.

However, Kathy must still log onto the network with network login name jsmith. To access her mailbox, she has her mail software connect to the mail server with POP username ksmith. John uses jsmith for both his network login and mail login.

Use with domains

An email address can be completely different from the name(s) of the mailbox(es) it goes to. This is primarily of interest to people with their own domains, who can have addresses in their domains mapped to mailboxes with unrelated names. For example, if John and Kathy have a business selling birds with domain birds.com, they can have email address sales@birds.com delivered to one of their mailboxes - or even both mailboxes.


Also, although Kathy's mailbox name is ksmith, she could have her email address be kathy@birds.com. Then ksmith would be the mailbox name she would use as a POP username to receive her mail, but kathy@birds.com would be the email address she would give people to use to send mail to her.


All domains have a default mailbox. If not otherwise specified, all mail to birds.com would go to a particular mailbox. For example, all birds.com could go to ksmith@idiom.com except for john@birds.com email that gets delivered to jjones@idiom.com.