There is also one more thing, related to gmail, i think they have disabled using 3rd part apps that could access their services, but there is a workaround
Can you try using port 587?
Because I have it working just fine … I use my own gmail account in the SMTP Requires authentication, but replaced my normal password with the app password.
Than I got a STRATLS error. That it’s start with an unexpected string or something like, that it’s not infornt of me but I tried to use this port as well. I realized I have mailbox for my domain. I’ll try to use my domain provider’s SMTP service.
We have it working with smtp-relay.gmail.com as the server
port 587
Use SSL is ON
Authenticated as a regular user (or perhaps with an app password, can’t see)