one MX record points to many A records - and only one MX record in domain

[Kevin Darcy]

David Rees wrote:

> Do you think this might cause anybody any problems - rather than have
> many MX records with one A record for each?
>
> Query: uk.mcd.com.      Query type: MX record
> Recursive query: Yes    Authoritative answer: Yes
> Query time: 328 ms.     Server name: n/a
>
> Answer:
>         uk.mcd.com.     3600    MX      10  mc.va3.ummail.com.
>
> Authority:
>         mcd.com.        3600    NS      bigmac1.mcd.com.
>
> Additional:
>         mc.va3.ummail.com.      2268    A       66.187.242.16
>         mc.va3.ummail.com.      2268    A       66.187.242.17
>         mc.va3.ummail.com.      2268    A       66.187.242.18
>         mc.va3.ummail.com.      2268    A       66.187.242.19
>         mc.va3.ummail.com.      2268    A       66.187.242.20
>         mc.va3.ummail.com.      2268    A       66.187.242.21
>         mc.va3.ummail.com.      2268    A       66.187.242.22
>         mc.va3.ummail.com.      2268    A       66.187.242.23
>         bigmac1.mcd.com.        3600    A       152.140.28.201

Yes, that works, but the sort order for round-robin A records is
undefined and different implementations behave differently. When caching
servers regurgitate this RRset, they'll regurgitate it in all sorts of
crazy ways and this may cause unwanted spiking. Multiple MX records can
have different priorities and therefore give you some degree of control
over your own fate. If the world could be persuaded to abandon
MX records in favor of SRV records (I'm dreaming, I know), then we could
use weighting to provide even more fine-grained control...


- Kevin