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Came across a deployment with the following 2 issues:-

  1. federated partners were showing up as presence unknown
  2. unable to call voicemail (hosted in O365)

When trying to send messages to these “unknown” federated partners I got “This message wasn’t sent due to company policy”.

So why did I try to message a contact with a presence status of “unknown? Simply because the federated contact could see my users presence and send me IM’s, I was even able to respond to these IM’s although the presence was still “unknown”.

Presence Unknown


A quick look at the client side logs revealed an error in the presence Subscribe message

Via: SIP/2.0/TLS;ms-received-port=24164;ms-received-cid=FC9300
ms-diagnostics: 1008;reason=”Unable to resolve DNS SRV record“;domain=”ucsorted.com”;dns-srv-result=”NegativeResult”;dns-source=”InternalCache”;source=”access.ucsorted.com”
Server: RTC/6.0
Content-Length: 0

Taking a look at the users (client side) local event log I found the same error.

Event Log

Event ID 11
A SIP request made by Lync failed in an unexpected manner (status code 80ef01f8).

Response Data
504  Server time-out
ms-diagnostics:  1008;reason=”Unable to resolve DNS SRV record“;domain=”ucsorted.com”;dns-srv-result=”NegativeResult”;dns-source=”InternalCache”;source=”access.ucsorted.com”;OriginalPresenceState=”0″;CurrentPresenceState=”0″;MeInsideUser=”No”;ConversationInitiatedBy=”6″;SourceNetwork=”5″;RemotePartyCanDoIM=”Yes”

Clearly there is some issue with either the federation SRV record or resolving the federation SRV record.

Checking the SRV record from the Edge server I can see that this record is not found. Checking the DNS for the Edge server I noticed that the interfaces are pointing to the internal DNS servers.


We have 2 options here:-

  1. Configure the Edge Server to point to a public (external) DNS server where the SRV record for _sipfederationtls._tcp.domain.com is valid (frowned upon by some security folks)
  2. Add the SRV record for _sipfederationtls._tcp.domain.com to the internal DNS, making sure that the target FQDN is the Public Access FQDN of the Edge Server.


Here is a little reason why you may want to avoid using the common sip.domain.com DNS name for your Edge Servers Access FQDN (only..). Internally the sip.domain.com record was generally configured to resolve to the front end pools, if we now need an internal SRV record for _sipfederationtls._tcp.domain.com then targeting this to sip.domain.com will simply get to the Front End Pool and not to the Federation point at the Access Edge FQDN.