None
Sending not allowed.
Smtp
Allow sending via SMTP only.
HttpApi
Allow sending via HTTP API only.
SmtpAndHttpApi
Allow sending via SMTP and HTTP API.
EEInterface
Allow sending via the website interface only.
SmtpAndInterface
Allow sending via SMTP and the website interface.
HttpApiAndInterface
Allow sendnig via HTTP API and the website interface.
UseAccessLevel
Use access level sending permission.
All
Sending allowed via SMTP, HTTP API and the website interface.