DTMF is not working in Lync conferences

http://tomtalks.uk/2014/04/join-a-pstn-call-requiring-dtmf-menu-tones-to-a-lync-conference/

EWS issues in Lync client

http://uc-dude.com/2014/05/27/complete-guide-for-troubleshooting-lync-outlook-clients-integration/

In one of my cases, the solution was to make string of internalEWS empty in registry

 HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Lync\sip_address@domain.con\Autodiscovery/InternalEwsUrl

Lync will be renamed to Skype for Business

http://blogs.skype.com/2014/11/11/introducing-skype-for-business/

Force to add Lync contact in Skype

if Skype users can not find Lync used by sip, it may be that federation is not yet established or have some other issue.

To force skype client to add a lync contact even if it's is not discoverable by seach, in IE type

skype:2:sip@address.of.contact.com?add