I changed MX records at my domain name provider (network solutions) twice today. One test client is still sending mails to the older record even though its TTL has expired. So, in other words, this is what happened:
Changed MX records to point to messagingengine.com at 10 AM (did not send any test mails via this server)
Changed MX records to point to zoho.com at 11:30 AM
At 1pm test emails from most client work via zoho, but 1 client that is using Microsoft Exchange still trying to send to messagingengine.com
At 2:30 pm test emails from the MS Exchange client STILL trying to go to messagingengine.com
The TTL for messagingengine.com is 1 hour, so it is long expired.
However, when I do an NSLOOKUP, it gives the non-authoritative answer correctly as zoho, but gives no authoritative entry. It is just blank. In other words, the nslookup says "Authoritative answers can be found from:" and then nothing. Here is what it looks like (identifiers redacted):
I think the problem must be that the record maintained by Network Solutions is somehow defective so that it is not identifying itself as the authoritative server somehow.
What really mystifies me is how the MS Exchange client could have gotten the messagingengine.com domain, since I did not send any test emails during the (short period) that my DNS records was pointing to that domain.
How can I fix this problem?