On 7/26/12, Lou Katz <lou@metron.com> wrote:
One of my users has reported incoming mail failures, which I finally tracked down. It turned out that Hotmail has seen fit to send the mail to his domain's A record machine, despite the fact that he has valid MX records.
You looked in the mail headers and saw hotmail's mail server do that, or the From address/return path just happens to be hotmail? I would ask for a specific example of a domain name in which that seems to happen, and exact DNS zone contents. I am sure that Hotmail does not ignore MX in general, unless they just broke something; many domains require MX processing and A record to properly be ignored for mail to be accepted. But there may be something else going on with a specific domain or DNS queries/responses from its nameservers, that results in MX being ignored or unavailable, resulting in a fallback to 'lookup A'. An example could be some dns issue such as slow response to MX query, 'MX to a CNAME', 'MX to an invalid label that looks like an IP', MX DNS response packet too large, .... -- -JH