Introduction Secure Mail Gateway

Description Mail-Gateway / Principle

If you regularly send large amounts of e-mail from your e-mail server, anti-spam databases can quickly put them on the list of unwanted senders - in other words, they will be set to blacklisted ("blacklist"). In that case, the IP address from which the allegedly unwanted emails are sent is classified as untrust and emails sent from there are no longer delivered.

To avoid such unwanted consequences, the Open Telekom Cloud works with a Secure Mail Gateway service. This service ensures the official and secure delivery of outgoing e-mails and prevents their inclusion in that called blacklists, the various blacklist providers. The original IP address of the sender is not directly recognizable because the Secure Mail Gateway always carries out the communication.

For security reasons, only this type of e-mail communication is activated in the Open Telekom Cloud.

The Secure Mail Gateway is the interface for sending mail from the Open Telekom Cloud to the Internet. The Secure Mail Gateway environment consists of three mail servers, which are distributed over three locations for redundancy. The locations are: eu-de-01 / eu-de-02 / eu-de-03

Scope of Service

Included Services:

  • Anti-Virus und Anti-Spam

  • Good Bad Gateway


In order to ensure the reliability and performance of the Secure Mailgateways, the mailing per customer can be limited to 100 Mails/min. In case the limit is activated and exceeded, the sender will receive the error message: „451 Ratelimit reached“. The limit is not active by default.


Due to the availability of the target systems, no guarantee can be given for delivery in time. ISPs may discard or lose email messages; recipients may have mistakenly given an incorrect address or ISPs may reject or tacitly reject the message if the recipient does not want to receive it.