This post is basic knowledge for people with non technical administration experience.
There are two parts to an email server, one that sends email to other servers, and one that enables your client to receive email from your local mailbox server. This is often the most confusing part to understand.
A mail client, either web based, or application based, uses both parts of the mail server to send and receive email.
Let’s start with sending of email. The sending of email is done via the outgoing mail server, most commonly known as the SMTP server. This is often provided by the ISP that your internet connection is connected to. The security method here is relay by IP address, so there isn’t any authentication method such as a login and password.
When you are using a 3rd party SMTP server, the most common security method for access is, SMTP AUTH. This is done by selecting the option for your mail client’s outgoing mail server, “My server requires authentication” and entering a user name and password – often the same as the pop3 client’s login information.
Once the message is sent, it is routed to the destination email address’s mail server. This mail server will route it to a mailbox as instructed in the email configuration files. the mailbox, accessed via a pop3 user name and password is unique to the local server.
The pop3 server, mostly referred to as the incoming mail server, is accessed with a pop3 login account name and password. This allows access to the mailbox file. The mailbox file contains a list of all email messages in the box. If two users shared the same mailbox user name and password, the could see each other’s email. This is coming when multiple people work under the same account, say – email@example.com.
If you want to separate email for a different group, example, firstname.lastname@example.org, this address will require it’s own email account to keep the email separate from the info mailbox.
The key item to remember is this, pop3 mailbox account can be used by many domains, it is simply a mailbox that can have one or many email addresses.