Orirginal source address after SNAT - SMTP

Hello all,

 

not sure if this question fits here; please correct me otherwise...

 

 

We are implementing bigips for smtp services. The current setup is one where the clients access the smtp servers "directly". What I mean is that client source addresses are visible on the mta and in the mta logs. This way we can see which client address originated any smtp message.

 

The bigips in our new architecture are not in the same segment as the mta's, so we need to use SNAT, because of connectivity between servers behind the bigips. Lets just say we cannot do without SNAT.

 

Only problem now is that the mta logs only show the self-ips of the bigips as origin for all smtp messages. No way to determine which client is responsible for the smtp messages anymore.

 

 

Is there a way (Like with the http x-forwarded-for header) to preserve the original source address of an smtp packet, so the mta logs start making sense again?

 

 

All help seriously appreciated.

 

 

Wouter de Bruin