Communicator Phone Edition uses the following DNS domains when querying information in DNS.

• SIP domain = Right side of sign-in address
  
  
• SMTP domain = Right side of primary e-mail address
  
  

If the query fails, Communicator Phone Edition tries to look up the same record with DNS suffix(es) appended.

• host.<SIP domain>
  
  
• host.<SIP domain>.<DNS suffix>
  
  

When Communicator Phone Edition connects to Office Communications Server 2007 R2, it queries in the following order.

• Hosts and port pointed to by these SRV records
  
  
  • _sipinternaltls._tcp.<SIP domain>
    
    
  • _sip._tls.<SIP domain>
    
    
  • _sipinternal. tcp.<SIP domain>
    
    
• sipinternal.<SIP domain>:5061
  
  
• sipinternal.<SIP domain>:443
  
  
• sip.<SIP domain>:5061
  
  
• sip.<SIP domain>:443
  
  
• sipexternal.<SIP domain>:5061
  
  
• sipexternal.<SIP domain>:443