Barracuda vs Surgemail

>>I have a Barracuda and sell virus & spam filtering through it for
customers that have their own mail servers. If the Barracuda should die,
I want to provide in surgemail the mechanisms to route their email and
let these customers know what level of service/protection Surge would
provide until the Barracuda is replaced.

What does a Barracude do that Surgemail doesn't?