If this is the first time you've opened the Mail app, you’ll see a Welcome page. Select Add account to get started.
If you've used the Mail app before, at the bottom of the left navigation pane, select Settings 
, and then choose Manage Accounts.
Select Add account.
Choose the type of the account you want to add. In this case, select Exchange.
Enter Your email address on the next screen then click next.
You will be asked to enter your password on the next screen, but it will fail to authenticate.
On the next page fill out the fields similar to below using your account info. The Domain is ctgi.
After clicking the sign in button you will get the error below. Click the Advanced button.
It will bring up another window. Input your information in the fields. see below
Click the sign in button. If all the information is correct you will get a security policy dialog, click yes to add the account.
On the next page click Done to complete the account setup
If email setup fails after going through these steps, send an email to the helpdesk at helpdesk@connecticutgi.org.