Are there any plans for IronPort to implement Sender Rewriting Scheme in AsyncOS? I'm personally not a big fan of SPF and SRS, but like it or not they're being deployed. We use a C300 to operate a mail forwarding service for our alumni (we get the forwarding data via LDAP), and I just finished working a problem that turned out to be caused by the fact that this forwarding service doesn't do SRS.
If SRS is in the works, then please for the love of all that's good and right in the world, include some option to check the original sender domain for an SPF record before performing any SRS mangling on it.
I do not know if Email Security Appliance(ESA) Product Management team is scoping this out and planning to implement it in a future release of the AsyncOS, but here is more information on Sender Rewriting Scheme(SRS) for those that are curious.
I would recommend that if you are proponent of SRS, that you send an email or communicate to your IronPort sales representative or system engineer that benefits of having SRS. This is the most effective way to get ESA product management to pay attention and to become aware of your wants.