Ok, this should be straight forward and I'm ashamed I haven't been able to figure this one out for myself, but...
I've recently discovered Amazon Route 53 DNS services and I'm now using this for the domains which I manage. In order to sanity check my MX records, I use MXToolBox.com to show the MX records and run a quick SMTP check on each MX server.
Here's an example of one of the domains in Route 53:
However when I try to run the query
mx:nylandconstruction.co.uk on MXToolBox.com, I am [what seems to be] redirected to the query results for
a:nylandconstruction.co.uk and the MX records are not returned:
So I check from command line:
$ dig nylandconstruction.co.uk MX +short 10 mx01.nylandconstruction.co.uk 15 vps02.aws.joe.nyland.tk.
Which confirms that the MX records are present.
If I query MX servers for gmail.com, MXToolBox.com behaves correctly:
So it appears that it's only my domains that are not returning valid MX records to MXToolBox, at least.
Does anyone have any ideas why? Does the above work correctly for anyone else using Route 53 for their DNS?