it was my fault, you cannot edit this data via the web interface.
As you said, you have to set this options on
smtp_address = "smtp.gmail.com"
smtp_port = 587
smtp_domain = 'gmail.com'
smtp_user_name = "firstname.lastname@example.org"
smtp_password = 'your_password'
smtp_enable_start_tls = true
After that, you must run this command:
And check if you see the correct data on the Discourse Admin Panel > Email
We are going to update our Wiki, thanks for your report.
I hope it helps.