Does default e-mail port behave differently than custom?
You wouldn't get anything from port 465 at all as it's encrypted.

Various forms of encryption use various ports (not all the same port) and keep it that way to keep themselves identifiable. Some may do their own thing, but it's entirely up to them.

Here a quick list of providers and their various ports for reference.

Generic:
Unencrypted     25 (or 587)
StartTLS        587
SSL             465


Google:
SSL             465
StartTLS        587

Yahoo:
SSL             465