I configured a custom domain www.sinclairelec.com.au at Windows Domain Admin Centre at http://domains.live.com. I followed the instructions to create appropriate records at my Domain Registrar to point my domain name to Windows Live. This worked OK including the MX record, Proving Domain ownership by a TXT record and Server Trust using a TXT record. The status of my domain within the control panel is shown as active.

I have created two email addresses - one send and receives fine, the other can send mail but cannot receive mail, either from outlook.com, MS Outlook, Mac Mail - anything.

Some information:
* Email account that currently cannot receive mail (but can send) was working up until this morning (Australian time).
* No domains.live or DNS settings have been altered since original setup.

Can you please help me resolve this issue?
Please let me know if you need further information.