Premium users have the ability to send emails that go out from the Gleam platform via their own SMTP provider such as SendGrid or Mailgun.
Applications that support Custom SMTP:
Custom SMTP is setup at a global Site level under Site Settings > Advanced > Custom SMTP
You can configure:
Most of these settings will be supplied by your email provider once you set up an SMTP user.
Custom SMTP will replace any emails that Gleam sends with your own provider. This includes: