@boniface we're using FA with SendGrid in our DEV environment.
We are using the SMTP server mode.
You will need to:
Add you host and username from instructions in sendgrid. It is smtp.sendgrid.net and apikey for everyone
Add the password from your instance under that Change Password flipper button in FA
Make sure your default from address is registered in SendGrid as an actual domain and address that you can send from - I believe this is necessary for all SendGrid email, otherwise you could use them for SPAM
That's all we did and it worked for us.
Note since this is DEV, we are not using TLS or SSL security. But we will in QA and Production