Re: IPv6 isn't SMTP

["Fred Baker (fred)" <fred () cisco com>]

On Mar 25, 2014, at 8:31 PM, Cutler James R <james.cutler () consultant com> wrote:

> 3.  Arguing about IPv6 in the context of requirements upon SMTP connections is playing that uncomfortable game with 
> one’s own combat boots.  And not particularly productive.

That is one of my two big take-aways from this conversation. The other is that operators of SMTP MTAs should implement 
RDNS for them, which I thought we already knew.

To my knowledge, there are three impacts that IPv6 implementation makes on an SMTP implementation. One is that the OS 
interface to get the address of the next MUA or MTA needs to use getaddrinfo() instead of gethostbyname() (and would do 
well to observe RFC 6555’s considerations). Another is that, whether on an incoming or an outbound connection, when the 
application gets its own address from the OS (binary or as a character string), it needs to allocate more storage for 
the data structure. The third is that it needs to be able to interpret user@2001:db8::1 as well as user@dns-name and 
user@192.0.2.1. 

All things considered, that’s a pretty narrow change set.

Everyone here, no doubt, is clueful enough to implement RDNS for their MTAs. We know that there are people in the world 
that don’t implement it for IPv4. Yet, here we are, using SMTP/IPv4 to discuss this, and I don’t hear anyone saying 
that IPv4 isn’t ready for prime time as a result of the fact of some operators not implementing RDNS.

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