Click on the "Mail" option at the top and Select Preferences
From the top tabs, select Accounts >> Click on the "+" to add a new account >> On the new window, put down your email address including @domain.com and the password, press Continue
On the next window, Select IMAP as the account type, in the Incoming Mail server, put your domain (If it is resolving) or the server hostname like (khanika.ethii.com, natasha.ethii.com etc.)
Fill up the Username with the @domain.com, if you have added an email account with the name "testing" then put [email protected] in the username section where domain.com is the domain you used to create that email account.
On the next window, select "Use secure sockets layer" and use Password as Authentication.
On the next window, put the same name you used for the incoming mail server in outgoing mail server, it can be mail.domain.com or domain.com if they are resolving or the hostname of the server.
Make sure to check the option says "Use Authentication", for username, fill it up with the full [email protected], if it is testing, then fill it up with [email protected], also make sure your password is correct.
On the next window, check the option says "Take account online" and press Create.
Note: It might say while verifing mail can't verify the identity of domain, please click connect when this window appears. It will appear if you do not have a trusted certificate purchased under your domain while using SSL port.