Re: History of fallback to A

Russ Allbery writes:
> For example, here at Stanford, there are a ton of departmental servers 
> that accept mail for some reason, and almost none of them have MX 
> records. People only add MX records when they need to direct mail 
> addressed to one system to a different one instead.
There are three cases:

1. The operators of such a server never add an AAAA. Nothing changes. MX 
lookups still fall back to A.
2. The operators of such a server add an AAAA at some point. IMO, adding 
MX at the same time is sound practice, but it's not strictly necessary, 
because there is an A and MX lookups still fall back to it.
3. The operators of such a server adds an AAAA and removes the A, or 
cannot get an A. In this case, an MX really has to be added.
Is this onerous?

Arnt