Keith Moore wrote:
Oh, I saw that message.  I just didn't see the consensus.
It wasn't a consensus, it was a unilateral statement based on the fact 
that there wasn't a consensus.
I think it was totally the wrong action.
There are two possible 'results' to the disagreement:
- No implicit MX. This causes me a problem with mail being delivered to 
me if I don't have an explicit MX record or an A record, only an AAAA 
record. This causes no mail to be delivered to me, so is easy to spot, 
and trivial to fix - I just need to add a single MX (or A) record
- Implicit MX. This causes me problems by (a) bunging up my mail server 
retry queue, and (b) loading my non-mail server hosts with the thousands 
of bounces to forged messages trying to be sent to them. (a) might be 
easy to spot, but is nearly impossible for me to fix (without 
'stretching' the standard - eg by having different retry algorithms for 
implicit vs explicit MC records), (b) is hard to spot what's happening 
without a packet tracer and knowing how to use one and is hard to fix 
since i need to do something to add 'non-MX' records to all my hosts, 
which could be hundreds of 'non-MX' records.
Now, which of those options sounds like it causes the worse problems?
'no implicit mx' may be slightly harder to implement in the mail server, 
but it IS *slightly*, and the cost of 3 or 4 lines of code isn't that 
much, so it isn't really much of an argument IMHO.