Stuart D. Gathman wrote:
On Tue, 19 Jul 2005, wayne wrote:
I think, in practice, that you will find very few cases of more than
10 MX records.
Actually, I run into this quite often. But not usually with
SPF records. When using best guess when there is no SPF record,
the domain will often have many MXs. Eg:
$ host -t mx netcom.com
netcom.com mail is handled by 5 mx06.netcom.com.
netcom.com mail is handled by 5 mx07.netcom.com.
netcom.com mail is handled by 5 mx08.netcom.com.
netcom.com mail is handled by 5 mx09.netcom.com.
netcom.com mail is handled by 5 mx10.netcom.com.
netcom.com mail is handled by 5 mx11.netcom.com.
netcom.com mail is handled by 5 mx12.netcom.com.
netcom.com mail is handled by 5 mx13.netcom.com.
netcom.com mail is handled by 5 mx00.netcom.com.
netcom.com mail is handled by 5 mx01.netcom.com.
netcom.com mail is handled by 5 mx02.netcom.com.
netcom.com mail is handled by 5 mx03.netcom.com.
netcom.com mail is handled by 5 mx04.netcom.com.
netcom.com mail is handled by 5 mx05.netcom.com.
Slightly off topic, but I'll take a guess and say that this was
someone's idea of load balancing. Not real bright IMHO. If you do a
dig, you can see that BIND only returns only returns 8 of the addresses
in the "additional information" section.
I guess what I'm trying to say is that just because people do use more
than 10 entries doesn't make it right. I believe the 10 limit is more
than sufficient.
However, to get back on-topic, since people DO do this type of thing,
perhaps a note in the FAQ (is there a FAQ?) regarding the use of more
than 10 records for any particular mechanism won't be handled in a
predictable manner or may even invalidate their SPF record altogether.
From the 2 cents department,
-=Jeremy