There are a few key terms that we use when discussing email and how it works. Some of the most useful are listed here.

Email service - Companies offer email services that enable account holders to send, receive and review email. Messages can usually stay on the provider's server (in the cloud) or be downloaded to a computer. Most providers also offer contact management, spam filter, the ability to send and receive attachments, and the ability to forward your mail to a different service. Today, almost all email services are Webmail services meaning that they offer the ability to use a web browser such as Firefox, Chrome, Safari, or Edge to access your mail. To use the webmail interface, you point your browser to the provider's website URL (such as http://gmail.com) and sign in with your email account and password.

Email forwarding service - An email forwarding service automatically redirects all email sent to your address at the service to another email address that you specify, in essence passing the messages on instantly to their final destination. Email forwarding services don't store your email. You can use an email forwarding service to have an address that remains stable even if/when you change the email service that you are using: you simply "point" the forwarding service to the email service of your choice. ASU's Electronic Post Office (EPO) is an email forwarding service that has a domain of @asu.edu. Even if you use a forwarding service you can optionally tell your contacts your direct email address and they can send mail directly to it, bypassing the forwarding service.

Email account- An email account gives you access to services at a particular email service. Your account with an email service is very often also your primary email address on that service, but can be something different. An email account has an associated password.

Email address - An email address uniquely identifies both the email service or email forwarding service that you are using and your mailbox or forwarding instructions as provided by that service. When email is sent to your email address, it's collected by your email service and placed in an inbox, which you access through your email account. Email addresses are always of the form: name@domain. The domain part is what is used to route email to your service and often matches the name of the service, such as @gmail.com or @outook.com. After the email arrives at the service, the name part of the address is used to see which account and associated mailbox should receive it.

Email app or program or client - You can use an email app that you install or that has been installed on your computer, tablet, or phone to access email on your email service. An email app must be configured with your email account and password in order to access your email. Some email apps are offered by email service companies and thus have the same name as the service, e.g. Gmail or Outlook. Others, such as Apple Mail, are not associated with a particular email service. Apps are not restricted to accessing mail from the same-named email service. For example, you can access a Gmail account from an Outlook app. 

Email Protocols are what email services use to communicate with each other and with your device:

• SMTP (Simple Mail Transaction Protocol) is used for sending email.
• IMAP (Internet Message Access Profile) is used for receiving email. When this protocol is used, messages stay on a mail server.
• POP (Post Office Protocol) is also used for receiving emai. When this protocol is used, messages are transferred to your computer and do not stay on a mail server.
• Exchange/MAPI (Message Application Programming Interface) is Microsoft's protocol that allows programs to become email-aware. While MAPI is designed to be independent of the protocol, it is usually used to communicate with a Microsoft Exchange Server.