MTA feature list
I investigated how DNS queries and SMTP deliveries are done concurrently
on each implementations.
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) |
| 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)
Copyright Kyoto Motonori (motonori@wide.ad.jp)