But, according to RFC 821, wouldn't 221 be a more appropriate response to a
QUIT?
Here's the relevant line from the RFCs list of reply codes:
221 <domain> Service closing transmission channel
250 (which is listed as "Requested mail action okay, completed") would
definitely also apply, but 221 does seem to be a more appropriate response.
And, if there are two correct answers, one of which produces an error and
one of which doesn't - it seems like the one that doesn't is better.
Just my opinion...keep up the good work.
P.S. I can't think of _anything_ that might be causing this, other than
that the remote server expects to receive "221 bye" when it says "QUIT"
and receiving "250 bye" confuses it into thinking the message
hasn't been delivered.
Also, the remote server in question is apparently version
5.1.0.78; courier can apparently accept messages from VINES 5.1.0.89
without problems.
If that's true, there are at least two things wrong with this:
* Any 2xx is defined as a positive response. The 2nd and 3rd digit, and
the descriptive text are for debugging purposes only
* The message is considered to be delivered after the 2xx response to DATA
is received. End of story. What happens subsequently to QUIT is
completely irrelevant.