Enhancements to the SMTP relay service

Google have launched several enhancements to the SMTP relay service. Admins will benefit from the following key features:

• Multiple authentication configurations: Admins can now configure multiple sets of authentication rules. For instance, you can specify that messages sent from one IP address are always allowed, messages from another IP address are only allowed if encrypted with TLS, and messages from another IP address range require SMTP AUTH.

• SMTP AUTH: This newly supported authentication method uses Google “application-specific passwords” to allow admins to configure clients to authenticate to the relay service. This feature is available for registered Google Apps users only.

• IP range description field: To manage IP addresses more efficiently, admins can enter descriptions in text fields for each IP address or range that you use to set authentication rules.

• Selective enable/disable of IP ranges: Admins can selectively enable/disable IP ranges approved for relay as needed

More information:
https://support.google.com/a/answer/2956491