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