David MacQuigg wrote:
Forget about DKIM. What if there is some other reason to abort, like
the payload is too large? We cannot just continue receiving data
forever. Is there a "permissible" way within SMTP to abort during
data, or should I just ignore these ambiguous requirements, and
either: 1) Send a TCP reset, or 2) Let the transmitter hang.
I would just continue accepting the message, and throw away the data,
then give a 'message too big' error at the end.
I suppose you could try to be clever and do a grey-listing-style thing
of recording the IP address, sender & recipient, and dropping the
connection, then when the retry is done, reject the message before the
data is sent - but I wouldn't be too confident about the reliability of
VPOP3 - POP3/SMTP/IMAP4/Webmail Email server for Windows