This class implements an abstract SMTP proxy - it serves as a starting point for customized proxy classes, but is itself not directly usable. Service definitions should refer to a customized class derived from AbstractSmtpProxy, or one of the predefined proxy classes.

The following requests are permitted: HELO; MAIL; RCPT; DATA; RSET; QUIT; NOOP; EHLO; AUTH; ETRN. The following extensions are permitted: PIPELINING; SIZE; ETRN; 8BITMIME; STARTTLS.