MTA feature list

Feature list of MTAs on message delivery with SMTP.

MTA	DNS Conc	SMTP Conc	SMTP Pgb
exim-2.053	No(ad)	Good(fork)	Excellent(MX)
postfix beta-19990122-pl01	Good	Good(fork)	Poor(domain)
qmail-1.03	Good	Good(fork)	No
sendmail-8.9.3	No(part)	No	Good(MX list)
smail-3.2.0.101	No(ad)	No	Poor(domain)
SMTPfeed-0.95	Good(ad)	Good	Excellent(MX)
zmailer-2.99.50s11	Good	Good(fork)	Poor(domain)

• DNS Conc - Concurrency of DNS queries (MX RR or A RR)
  • Good - Concurrent
  • No - Sequential

  • ad - Additional Informations are used effectively
  • part - MX RR queries are made concurrently before any SMTP deliveries, A RR queries are made just before establishing TCP connections.

• SMTP Conc - Concurrency of SMTP message deliveries
  • Good - Concurrent (in one process)
  • Good(fork) - Concurrent (with multiple processes)
  • No - Sequential

• SMTP Pgb - Fineness of SMTP Piggybacking
  • Excellent - Par member of MX RRs
  • Good - Par sequence of member of MX RRs (hostsignature - sendmail term)
    A sample of MX RRs which will cause piggybacking (values of preferences should not be equivalent -- sequence is important

          domain1 IN MX  1 mxhost-A
                  IN MX  5 mxhost-B
          domain2 IN MX 10 mxhost-A
                  IN MX 20 mxhost-B 

    A sample of MX RRs which will NOT cause piggybacking

          domain1 IN MX 10 mxhost-A
                  IN MX 20 mxhost-B
          domain2 IN MX 10 mxhost-A
                  IN MX 20 mxhost-C 

  • Poor - Par domain part of e-mail address
  • No - No piggy backing (even multiple addresses are unique)