A records point to a domain

[stanislav shalunov]

Stewart Tolhurst <news at stolhurst.freeuk.com> writes:

> yahoo.com A (Address) 204.71.200.243
> Is this kind of thing RFC compliant?

It most certainly is.

> Does it raise any issues or cause any potiential problems?

A lot of people do it.  (I do it, too.)

The only problem I can think of is the following scenario:

1. You have `example.com. MX 10 mail.example.com.',
   `example.com. A 10.0.0.1', and `mail.example.com. A 10.0.0.2'.

2. A remote MTA tries to deliver an email message to user at example.com.

3. It does an MX lookup on `example.com.' and it fails (e.g., because
   the host can't get your nameservers).

4. Since it didn't get an MX record, the MTA looks for an A record.
   By this time it can get to your name servers so it think that you
   want mail for user at example.com to go to 10.0.0.1 rather than
   10.0.0.2.

5. You happen to run something on port 25 on your web server, but it's
   not configured as a mail exchanger for your site, so it gives a
   permanent error and the message bounces.

In the end a perfectly good message that should have been delivered on
the next queue run is bounced because you had an A record and an MX
record for the same thing, pointing to different machines.

I'm not sure which MTAs would and would not go to step 4 when a
temporary DNS failure occurs.  Anyone?

-- 
stanislav shalunov				| Speaking only for myself.