But Does it lose mail?

NO..

We've had numbers of "complaints" since we announced this. once we get the bounce, inevitably it's something else (transient DNS failures, Someone else's dead server, Broken viruswalls elsewhere, other PEBKAC and ID-TEN-T issues)

For the first couple of months we hard pressed to find a genuine failure (delayed mail, yes, failures, no)

Then we did!

Some versions of Novell, and Cruddy Symantec viruswalls like to do a RSET randomly after HELO. Spamd didn't implement RSET until we found this.

Given that two months were required to find a real case, we suspect they are not very common