Can I use Gmail, Yahoo, or Hotmail to receive trigger policy notification?

No you can’t. The reasons are explained below:

Free Yahoo Email and Hotmail does not provide standard SMTP protocol, while Gmail requires TLS (some kind of encrypted transmission) which we don’t currently support.

There is currently no plan to support these free Email types.

You need to find a mail server that supports SMTP protocol without TLS requirement. It’s generally the case of corporate internal mail servers, not those free Email servers which (due to being the main target of Email abuse or spamming) requires higher security.