Out of the blue over the weekend, something strange has happened to my email server at work, as it suddenly stopped receiving emails. This has nothing to do with the server, but more to the fact that my mail.mydomain.com was being ignored.
Ping tests to mail.mydomain.com stopped working, although other.mydomain.com continued to work fine.
I've spent three hours on the phone to my ISP (BT) about it, and they couldn't help, except to find that it wasn't their fault.
As a workaround, I've used the 'other' A record (within my domain name DNS settings) to do what I need it to do (including adjusting my MX record accordingly), but despite deleting and re-adding the 'mail' A record, the mail.mydomain.com simply will not ping correctly, whereas other.mydomain.com will (both end up at the same machine on my network).
The TTL on the DNS settings for the domain name is 86400s, so maybe it's a waiting game, but having not changed anything on the domain name DNS settings for at least a year, it seems odd that such a thing would happen.
Any suggestions as to where I need to look to investigate further?