MX Record Theories

gb10hkzo-nanog at gb10hkzo-nanog at
Thu May 28 03:40:29 CDT 2009

On Wed, 27 May 2009 09:48:39 -0400, <gb10hkzo-nanog at> wrote:
> Actually, I was thinking to myself yesterday that the email world is going to be awfully
> fun when IPv6 sets in and we're all running mail servers with nice long AAAA records such as
> fc00:836b:4917::a180:4179.

> You do realize DNS queries aren't passing around addresses in ASCII?  3 additional bytes per address isn't going to break the bank.

I think you might have missed the point of my post.

It was a tounge in cheek reply to the poster who suggested bad things happen if the DNS message size exceeds 512 bytes.

He was commenting about AOL's MX records which currently weigh in at 507 bytes.

Therefore if we were to hypothesise that the world ends at 512 bytes, then companies doing things the way AOL does, but using IPv6 addresses rather than IPv4 addresses for their MX records could run into "problems".

Hope that clarifies :)


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