class EmlServer(SMTPServer):
    no = 0

def process_message(self, peer, mailfrom, rcpttos, data):
    filename = '%s-%d.eml' % (datetime.now().strftime('%Y%m%d%H%M%S'), self.no)
f = open(filename, 'w')
f.write(data)
f.close
print('%s saved.' % filename)
self.no += 1

def run():
    foo = EmlServer(('localhost', 25), None)
try:
    asyncore.loop()
except KeyboardInterrupt:
    pass
if __name__ == '__main__':
    run()
a simple smtp server