Step 1 » Open Mail and select Add Account from the File menu at the top of the screen.
Step 2 » Enter your name and email address, then click Continue.
Step 3 » Select IMAP as your Account Type and enter your server address, username and password. Make sure your full email address is listed for the username. Click Continue.
Step 4 » You will receive a warning message asking you to Verify Your Certificate for mail.yourdomain.com. Click CANCEL.
Step 5 » Click Continue to skip to the next step.
Step 6 » Make sure "Use Secure Sockets Layer" is un-checked. Set Authentication to Password, then click Continue.
Step 7 » Enter your Outgoing Server settings. Select the box labeled Use Authentication and enter your username and password. Click Continue.
You will receive a password security warning. Click Setup Manually.
Step 9 » Make sure Use Secure Sockets Layer is un-checked. Set Authentication to Password, then click Continue.
Step 10 » Review the Account Summary screen, and click Create to finish setting up your mailbox (make sure the "Take account online" checkbox is selected).
Step 11 » Select Preferences from the Mail menu at the top of your screen.
Step 12 » Choose the Accounts tab and select your account in the list of accounts (on the left). Select the Mailbox Behaviors tab and make sure all options are un-checked except for "Move deleted messages to the Trash mailbox".
Step 13 » Close the Accounts window to save your changes.