Exchange 2010 AutoDiscover - DNS Configuration - SRV Record

You can use Nslookup against a public dns server to verify if the record is correctly configured. 

1)      In the command prompt type nslookup

2)      Type set type=srv

3)      Type _autodiscover._tcp.tenant1.com

 

Server:  hostname.anydomain.com

Address:  10.0.25.5

 

Non-authoritative answer:

_autodiscover._tcp.tenant1.com      SRV service location:

          Priority       =  0

          Weight       =  0

          Port             =  443

          svr hostname  = mail.contoso.com

 

mail.contoso.com internet address = 10.0.25.6

 

Exchange 2010 Multi-Tenant AutoDiscover and DNS Configuration:

http://social.technet.microsoft.com/wiki/contents/articles/5787.exchange-2010-multi-tenant-autodiscover-and-dns-configuration.aspx