Support - MailBoxes vs. Domain Email Addresses

MailBox:

A MailBox is a physical location on our mail server.

This is where your email messages are ‘physically’ received (or kept until you check your mail) much like mail going to a PO Box at the post office or to your home.
Your MailBox username is frequently referred to as your 'User Name' in your email client (like Outlook) or, 'UserID' in the Adhost Webmail.

Domain Email Address (aka your email address):

Your domain email addressis simply your email address.

This is what you would give out to others so they can email you, like "joesmith@mywebsite.com".
This is similar to writing an address like 140 4th Ave N, Seattle, WA 98109 on the front of an envelope. This tells the postal person WHERE (the physical location) to deliver the letter.

How It Works on the Internet:

When a user composes an email message to you, they indicate who they want the message sent to by addressing the envelope with something like "joesmith@mywebsite.com".

When our mail server receives this ‘envelope’ with your email address (email alias) it looks for a “Domain Email Address” file for your domain (mywebsite.com)
The “Domain Email Address” file is a list of all the email addresses associated with your domain.
Once it finds your Domain Email Address file, it then searches for your domain email address in that file and delivers the message to your MailBox (your PO Box).
If it does not find your domain email address, it then looks for a catch-all.