I just registered an account on sendgrid, verified a single sender, setup a mailer in Wappler:
Setup a send mail step in the server action:
Email received in my gmail inbox …
So, you can use your single sender with the smtp relay as explained in their docs.
Really a straightforward process. You don’t need to install any sendgrid node modules or whatever.
Probably you messed something with installing these packages or trying to create custom modules - it just works the way explained above and it’s the first time i am using sendgrid.