We use it internally, but keeping conversations together with context in place as we move between devices during our business day has proved inconsistent at best and maddening at worst when conversation pieces that have timely significance are lost in the interweb, not surfacing until they show up in Outlook's "Missed Conversations" folder (a great feature but another thing that needs education of the end user). But with the right education, training, and product development focus. Skype for Business server 2015 or Lync Server 2013 Lync Server 2010 can be used with all the latest updates installed, however Lync Server 2013 or Skype.
The Group Policy setting in question is SavePassword and is used to control the ability to prevent users from checking the 'Save my password' box. Lync Server 2013 also supports OAuth, but my guess is that there simply isnt. This means that you can see peoples Skype, Teams or Jabber availability, reply to an email via an IM or directly start a call or chat all from within Outlook. We have clients who LOVE it as an internal company instant messenger. We recently discovered an issue with the with the Lync 2013Skype for Business GPO (Group Policy Object) that controls a users ability to save their password. configure oauth between skype for business server and exchange online. Both Skype and Skype for Business (previously known as Lync), Microsoft Teams as well as Cisco Jabber can integrate with the IM functionality available in Outlook. When users/companies tried to use it for that, there were sometimes issues with external end user Microsoft accounts and other gotchas. The meeting feature (along with screen sharing) was never widely adopted as WebEx and GoToMeeting. Lync is one of those Microsoft products that had SO much promise and SO many uses, but once again the lack of educating/training on those features along with inconsistent experience from workstation to phone made people abandon it after using it for long enough to learn all of the features.