Scot Stevenson.  Could be a bug fix candidate, but probably doesn't
matter much unless a certain blue-nosed cat suddenly becomes corporeal
and starts emailing some stmp.py (sic) fronted mailer.

Note:  There is a TBD (aka FIXME) for how best to handle the refused addresses

__getaddr(): Watch out for empty addresses that can happen when
something like "MAIL FROM:<CR>" is received.  This avoids the
IndexError and rightly returns an SMTP syntax error.

parseargs(): We didn't handle the 2-arg case where both the localspec
and the remotespec were provided on the command line.

set_reuse_addr() that does the setsockopt fiddling.  Use it instead.

so that it can be suppressed.

optional, and default to `localhost' and ports 8025 and 25
respectively.

SMTPChannel.__init__(): Calculate __fqdn using socket.getfqdn()
instead of gethostby*() and friends.  This allows us to run this
script even if we don't have access to dns (assuming the localhost is
configured properly).

Also, restore my precious page breaks.  Hands off, oh Whitespace
Normalizer!

NotImplementedError) found by Neil Norwitz's PyChecker.

also modified check_all function to suppress all warnings since they aren't
relevant to what this test is doing (allows quiet checking of regsub, for
instance)

I'm now checking it in.  I need to write some documentation for it,
but I don't have time right now.  Still, I wanted to get this into
2.1a2.

# Overview:
#
# This file implements the minimal SMTP protocol as defined in RFC 821.  It
# has a hierarchy of classes which implement the backend functionality for the
# smtpd.  A number of classes are provided:
#
#   SMTPServer - the base class for the backend.  Raises an UnimplementedError
#   if you try to use it.
#
#   DebuggingServer - simply prints each message it receives on stdout.
#
#   PureProxy - Proxies all messages to a real smtpd which does final
#   delivery.  One known problem with this class is that it doesn't handle
#   SMTP errors from the backend server at all.  This should be fixed
#   (contributions are welcome!).
#
#   MailmanProxy - An experimental hack to work with GNU Mailman
#   <www.list.org>.  Using this server as your real incoming smtpd, your
#   mailhost will automatically recognize and accept mail destined to Mailman
#   lists when those lists are created.  Every message not destined for a list
#   gets forwarded to a real backend smtpd, as with PureProxy.  Again, errors
#   are not handled correctly yet.