Open Mozilla Thunderbird and choose New… from the Hamburger menu.
Select Existing Mail Account in the Add New menu.
In the Set Up Your Existing Email Address page enter in your Display Name, your new Email Address, and the Password for this new Email.
Before clicking Continue, Select Configure Manually on the bottom left below the password field.
After selecting Configure Manually, fill out the expanded window with the following details, making sure that the Username is the new Email you are adding.
Under Incoming Server, set the Hostname to imap.caorda.com, set the Port to 993, and set the Connection Security to SSL/TLS.
Under Outgoing Server, set the Hostname to relay.caorda.com, set the Port to 587, and set the Connection Security to STARTTLS.
For both Incoming Server and Outgoing Server set the Authentication Method to Encrypted password.
Then, after entering in these details select Done.
After entering in the server details and selecting Done, Thunderbird will test the connection and when successful will send you to this welcome screen. From here you can click on Finish.