On Fri, 14 May 2004, Jon Kyme wrote:
Well you do seem very sure, so how do we explain:
Most MTAs will not 550 an invalid MAIL FROM because that prevents people
with broken setups from email postmaster to get help with their
communication problems. Instead they will 550 the subsequent RCPT TO
commands complaining about an invalid sender address.
:; telnet mx.cam.ac.uk smtp
Trying 131.111.8.4...
Connected to purple.csi.cam.ac.uk.
Escape character is '^]'.
220 purple.csi.cam.ac.uk ESMTP Exim 4.20 Fri, 14 May 2004 16:30:47 +0100
EHLO chiark.greenend.org.uk
250-purple.csi.cam.ac.uk Hello chiark.greenend.org.uk [193.201.200.170]
250-SIZE 104857600
250-PIPELINING
250 HELP
MAIL FROM:<abcd(_at_)e(_dot_)f(_dot_)g(_dot_)h>
250 OK
RCPT TO:<fanf2(_at_)cam(_dot_)ac(_dot_)uk>
550-Verification failed for <abcd(_at_)e(_dot_)f(_dot_)g(_dot_)h>
550-Unrouteable address
550 Invalid Sender Address
quit
221 purple.csi.cam.ac.uk closing connection
Connection closed by foreign host.
--
Tony Finch <dot(_at_)dotat(_dot_)at> http://dotat.at/