We are integrating GMAIL / GSUITE with a DLP system for a client. The E-Mail DLP module is postfix based. In the E-Mail DLP module I will add an X-HEADER, which I intend to read in the GMAIL forwarding rule to DLP to avoid an infinite loop. So the GMAIL forwarding rule to the DLP system should allow me something like this:

• If X-HEADER-DLP is not present, THEN forward message to DLP E-Mail Gateway
• Otherwise (if X-HEADER-DLP is present) forward E-Mail to recipient(s)

In MS Exchange I have the possibility to check for the incoming IP Address to avoid such next-hop loops, but as this feature in GMAIL is not available, I am trying to use the X-HEADER approach instead.