I'm running BIND 9.3.3rc2 on a CentOS 5 system acting as an SMTP server. Until last week, I haven't had any problems with DNS or name resolution. The only problems I have resolving are with subdomains for Microsoft's Outlook 365 service.
For our customers who are using Outlook 365, Microsoft has changed their MX server configuration from a generic mail.outlook.com domain to example-com.mail.eo.outlook.com where 'example-com' represents their registered domain (they change the dot to a dash). Sometimes 'eo' becomes 'protection' in this scheme. When a customer has an email at one of these subdomains, our SMTP can't resolve the name and the mail goes into the
If I run
dig example.com MX I get the following as output:
::ANSWER SECTION: example.com 3600 IN MX 10 example-com.mail.eo.outlook.com
So it finds Microsoft's subdomain for this customer, but I can't ping it or the root domain; they both return
ping: unknown host example-com.mail.eo.outlook.com
However if I dig this domain using Google's DNS server, I do get an IP address:
dig example-com.mail.eo.outlook.com @18.104.22.168 ;; ANSWER SECTION: example-com.mail.protection.outlook.com. 9 IN A 22.214.171.124 example-com.mail.protection.outlook.com. 9 IN A 126.96.36.199
I can statically add those entries to /etc/hosts, but this means being reactive. How do I need to configure DNS so that these entries will work? If they work for Google they must work for others as well.