First, go to ‘File’ and then ‘Account Settings’ and click on ‘Account Settings’ from the drop-down option.
The ‘Account Settings’ window should appear as below:
Select the account you receive email through and click the ‘Change’ button.
The following ‘Change Account’ window will appear. In the Server Information area, you will need to set Elastic Email's SMTP address. In Outgoing Mail Server (SMTP), you will enter smtp.elasticemail.com and under Logon Information, please enter your Elastic Email username and password (API key from your account).
Next, click on the ‘More Settings’ button and enter the information as shown below.
(Keep in mind you can also use port 25 with no security or 587 with TLS security.)
Under the 'Outgoing Server Tab', check 'My outgoing server (SMTP) requires authentication'. Click 'Log on using' and enter your Elastic Email Username and Password (API key located on your account). Click ‘OK’. This will return you to the ‘Change Account’ window.
Once back on the Change Account screen, click 'Next >' to test that everything is setup correctly.
If everything checks out correctly, you should see this: