...to the client address as this frees the RCPT strings to contain
just an email address and by passing the test number into curl as the
client address remains consistent with POP3 and IMAP tests as they are
specified in the URL.
This bug report properly identified that when doing SMTP and aborting
the transfer with a callback, it must be considered aborted prematurely
by the code to avoid QUIT etc to be attempted as that would cause a
hang.
The new test case 1507 verifies this behavior.
Reported by: Patricia Muscalu
Bug: http://curl.haxx.se/bug/view.cgi?id=1184