1.)If you are using Outlook 2010/2013
You will need to go to the "File" menu, and go down and click on "account settings," you will now be at the "account settings" screen.
2.)On the next screen, click on your account for your domain name (to highlight it) and then click on the "change" button*.
*(If you do not have an account listed here or if you want to create one in addition to your current email accounts you have, click on the "new" button to create one. Check mark the "manually configure" option and push the "next" button. Make sure the "internet email" option is selected and push "next".)
3.)On the "internet email settings" page, make sure all the fields are filled in with your information , and then click on the "more settings" button.
4.)On this new window, click on the "outgoing server" tab (at the top) and then make sure that "my out going server (SMTP) requires authentication" is checked. You can leave the bullet on "use the same settings as my incoming mail server" and click ok at the bottom.
5.)You will then want to click on the "next" button.
6.)After this is complete, click on the "finish" button.
You now should be able to send and receive messages. Press the "send/receive" button to confirm.