Bit Bucket for SMTP Traffic

I'm looking for a solution that basically accepts SMTP connections, but sends all mail to a bit bucket -- almost like a /dev/null. The problem im running into, is I cant just use a simple irule that "drops" or "rejects" the traffic. I would need to accept the connection and somehow find a way to spoof the initial EHLO response from the f5. Any suggestions would be greatly appreciated.