How to write iRules for log client IP in snat to smtp server?

Hi

 

 

All Experts. I have encountered a thorny problem in need of help.

 

 

In the past, to record the client IP in http server log. I can use enable X-forward or insert other header by iRules. But if server is smtp server. And forward data by snat.How to write iRules for log client IP in snat to smtp server?

 

 

Thank you!