On Wed, 2 Apr 2008, Arnt Gulbrandsen wrote: > If the ability to set up a mail server purely by setting up a host > (without adding an MX record) is a significant feature of the internet > mail system, then I would expect to see significant use of it. Right? > > So I took 30,000 recent messages containing little spam. In those > messages I found 954 unique domains in To, From, Cc and Reply-To > fields. Among the 954 domains, practically all have MX records and most > have A records. There are 38 domains that have an A record but no MX. > All 38 are reachable, 33 answer on port 80, 21 answer on port 25, and > some of the 21 seem to be incorrectly configured. > > So that leaves about 20 domains, 2% of the original. >
I checked my logs of the last 7 days. My mail servers have sent emails to 29.401 different domains worldwide, 29.015 via MX records and only 286 via A records, which is less than 1 %. For a statistik about how many emails are sent via MX records compared to A records the result would even be lower. The missing MX records for the 286 domains are the result of lazy or clueless mail administrators. The discussion here is about a standard, which means enforcing rules and not helping people to stay lazy. It makes no sense to transfer a feature which was needed 20 years ago but not anymore in these days to a new protocol. That means in the case of no MX record, I suggest the following algorithm: - if a domain has only A records, synthesize a MX record - if a domain has A and AAAA records, synthesize a MX record only for the A records, the AAAA records should be dropped. - if a domain has only AAAA records, do not synthesize a MX record For a MTA with ipv4 stack, this would mean no change. For a MTA with dual stack, only the ipv4 part would use synthesized MX records. A MTA with ipv6 stack only would never synthesize a MX record. Michael Storz
