This is a simple setup and yet I cannot send a test email. What I did is as following:

1. set up an outgoing mail server

1a. SMTP Server: mydomain.com (yes, this is same as my domain name)

1b. SSL/TLS enabled, Port 465

1c. username and password filled

2. Test connection successfully ("Connection Test Succeeded! Everything seems properly set up!")

3. Alias Domain is set to mydomain.com (Settings->Configuration->General Settings)

4. Going to Settings->Technical->Emails

5. Create a test email to send

6. After I click the "Send Now" button, it states "Delivery Failed".

What is wrong with this set up? It works fine if I use different SMTP server such as gmail but not my own hosting domain SMTP.