Open MacMail (also called AppleMail). Click on Mail in the top left, then click on Preferences.
Click the Accounts tab at the top of the preferences window. (Should default to the accounts tab.)

Make sure you're on the Account Information tab. Note the Account Type at the top.

Fill in the fields accordingly:
  • Description: Put the email address.
  • Email Address: Enter the full email address. (ex: john@bluevalley.net)
  • Full Name: Enter the desired display name.
  • Incoming Mail Server: mail.bluevalley.net
  • User Name: Enter the full email address. (ex: john@bluevalley.net)
  • Password: Enter the password for the email account. (If not already filled in.)
Click the Advanced tab near the top.
Fill in the fields accordingly:
  • Check the box that states Enable this account..
  • Check the box that states Include when automatically checking for new messages..
    Skip down to the bottom half.
  • Port: 995 for POP, 993 for IMAP
  • Authentication: Password
We now need to check the Outgoing SMTP settings. Click the Account Information tab near the top.
Near the bottom there is a drop-down menu for Outgoing Mail Server (SMTP). Click the small arrows to the right of the field and then click the Edit SMTP Server List... menu option.
The top half of this screen lists the SMTP servers setup in MacMail. If there's more than one here we may need to click on the appropriate one for your email account in this list. If there is no SMTP server at all, click the small plus + sign on the left to add a new one.

Fill in the fields accordingly:
  • Description: Put "mail.bluevalley.net"
  • Server Name: mail.bluevalley.net
  • TLS Certificate: (Not always there. Leave on None.)
Click Advanced.
Fill in the fields accordingly:
  • Select the Use default port (25, 465, 587) option
  • Check the box that states Use Secure Sockets Layer.
  • Authentication: Password
  • User Name: Enter the full email address. (ex: john@bluevalley.net)
  • Password: Enter the password for the email account. (If not already filled in.)
Click OK when finished editing the SMTP servers.
When all of the requisite changes have been made to all of the accounts, close the Preferences window with the small red dot in the top left. This will prompt MacMail to ask the user if they wish to save all of the changes they just made, they need to click Yes.
Incoming (IMAP)
Server: mail.bluevalley.net
Port: 993
SSL: Yes
Username: Your full email address

Incoming (POP)
Server: mail.bluevalley.net
Port: 995
SSL: Yes
Username: Your full email address

Outgoing (SMTP)
Server: mail.bluevalley.net
Port: 587
SSL: Yes
Authentication: Enabled