We are running Windows 2008 SBS Standard, which has been up for about 3 years. Email is flowing with the occasional hicup. On Monday a customer upgraded to Microsoft Office 365 and now hosts there email at Microsoft. Emails to that address are getting a delayed delivery message back to the user with the Last Error of:
451 4.4.0 DNS query failed.
I have tried:
- Testing the nslookup and it is returnning the A record fine.
- Have Flushed the DNS ipconfig /flushdns
- Cleared the DNS cache
- Tested the SMTP server from MXtoolbox and it is working although giving the warning:
Warning - Reverse DNS does not match SMTP Banner
- Even added a mx record to my local DNS zone for the domain.
Any thing else to try?