[fetchmail]How to reject at RCPT and drop message?

Hi, I'm running fetchmail release 6.2.4+NTLM+SDPS+SSL+NLS.  I'd like
to stop fetchmail at the RCPT stage and have it abandon the message. 
I've tried returning 550 and 553 but I get the same result with both:

fetchmail: SMTP> RCPT TO:<address I don't want to accept>
fetchmail: SMTP< 553 Address not accepted
fetchmail: SMTP error: 553 Address not accepted
fetchmail: SMTP listener doesn't really like recipient address `blah'
fetchmail: SMTP> RCPT TO:<fetchmailpostmaster(_at_)foo>
fetchmail: smtp listener protocol error
fetchmail:  not flushed
fetchmail: POP3> QUIT
fetchmail: POP3< +OK

What's the best way to stop fetchmail at the RCPT stage and delete the
message from the POP3 server?

Thanks,
Laurence