#Lync Question 9: How many SIP domains do I need

It is always recommended that a user’s SIP URI (Uniform Resource Identifier) matches their SMTP address for a consistent corporate identity also the simple things for users.

Where the SIP URI differ from the primary email address then the Lync client will warn that addresses don’t match and the following features are lost and/or receive the following errors:

  • Cannot view presence in Outlook.
  • ‘Cannot integrate with Outlook because Outlook mail profile is not configured correctly’ error message.
  • Cannot connect to Exchange Web Services.
  • Unable to pull Free/Busy information.
  • Communicator self-presence not updating per Outlook calendar.
  • ‘Cannot connect to Microsoft Office Outlook to open the desired folder.  Please close any open outlook dialog boxes and try again’ error message.
  • Unable to save Communicator or Lync Conversations to Outlook.

Also the DisableEmailComparsionCheck can be set to $true in the Client Policy then the Lync software will not attempt to verify that any currently running instance of Microsoft Outlook belong to the same user.  So be warned for any users with multiple mail profiles!

However this won’t help federated users as they will not be able to see presence through Outlook.

In order to determine how many SIP domain you need, first ask your email administrator which SMTP domains the mail system supports and then secondly how many recipients use each SMTP domain as the primary email (reply) address. This is important as secondary SIP URI’s aren’t supported and we don’t care if users are using SMTP domains as secondary addresses!

OK, next certificate costs, there are two certificates we need to consider:

  • External Web Services Certificate (Installed on the reverse proxy)
  • External Edge Certificate (installed on the Lync Edge Server)

With the External web services certificate, we need to consider:

  • Simple URL scheme (primarily the ‘Meet’ URL) but I won’t dig into this here
  • LyncDiscover, do you want to make things simple for user with Lync Mobile or have users manually configure Lync Mobile to be able to connect
  • Web Scheduler URL (see #Lync Question #3)
  • The number of Front-End and Director pools deployed within the topology
  • Oh and Exchange AutoDiscover and EWS, let’s leave that problem to the Exchange Admin 🙂

With the External Edge Certificate, we need to consider:

  • The Access Edge and Web Conferencing Edge FQDN as defined in the Topology (probably your based on your primary SIP domain)
  • Then if we want Auto configuration of client and Enhanced Federation we will need sip.domain1.com defined for each SIP domain
  • Then if you have multiple edge servers/pools within your topology I wouldn’t recommend you define your first access edge FQDN as sip.domain1.com use something else and use this base name for each of the secondary SIP domains (domain2.com) so you can get automatic failover (for DR) working via SRV priorities.

That’s the basic

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