smtp vrfy

[Simon Jones]

Hi, I'm trying to get my mailscanner box to check with the destination
server that the recipient address is valid using smtp vrfy.

I have implemented this in main.cf and it works great BUT it works for
ALL addresses on the destination server, i.e. I get 

550 5.1.1 <valid at domain.co.uk>: Recipient address rejected:
undeliverable addres
s: host xxx.xxx.xxx.xxx[xxx.xxx.xxx.xxx] said: 501 unacceptable mail
address (in rep
ly to MAIL FROM command)

when telnetting to the box on 25, however if I telnet to the destination
server and do the same I get:

vrfy valid at domain.co.uk
250 ok its for <valid at domain.co.uk>
vrfy rubbish at domain.co.uk
550 unknown user <rubbish at domain.co.uk>

If the destination server is working correctly how comes the mailscanner
box is telling me it's an invalid user?

I suspect the mailscanner box is checking locally? In which case it will
only allow to @domain.co.uk rather than user at domain.co.uk, but I'm not
sure yet :)

Thanks in advance

Simon