allow_smtp_auth_plain_without_tls

Optional boolean. Defaults to false.

When false, and the connection is not using TLS, SMTP AUTH PLAIN will be premptively failed in order to prevent the credential from being passed over the network in clear text.

You can set this to true to allow sending the credential in clear text.

Danger

Do not enable this option on an untrusted network, as the credential will then be passed in clear text and visible to anyone else on the network