TLS/STARTTLS and SSL Secure Connections
When sending emails, you can use TLS encryption or SSL encryption. If you can choose between the two, we suggest using TLS.
Using TLS or SSL is optional with SMTP2GO.
If you choose to connect using TLS (also known as STARTTLS), you can use the same SMTP ports as with non-secure connections: 2525, 8025, 587 or 25.
We normally recommend using SMTP port 2525 as it is open at almost all locations around the world.
If you choose to connect using SSL, you can use SMTP ports 465 or 8465.