Lync for Mac failing to sign in

October 21 - Microsoft Lync for Mac 2011 client update released today

This update addresses two known issues:

  • Lync for Mac sign-in into Office 365
  • Installation of Mac OS X Lion 10.7.2 causes Lync for Mac to become inoperable

The Lync for Mac client is supported with Office 365 however we have an issue under investigation where customers can’t sign in.



October 13 – 3rd workaround possibility

Updating October 12 with another workaround which might help you in the short term. We do recommend customers open support tickets for issues so we can track them and follow up accordingly. The only other thing I am hearing rumblings about is the use of VPN solutions possibly being a factor including ones that were working with Communicator for Mac. Cases like this benefit from as complete a picture as possible until we find the 1 or 2 key items.


  1. Updating with Microsoft article Originally I saw the solution from this 3rd party blog article about “Unknown” Keychain -
  2. Babul and I had a dialog starting from a Twitter question, thankfully he fixed the issue and also blogged the solution here regarding the requirement Lync has with Exchange configuration-
  3. The only way to get the client to login, is to try login in with a bad userid for example: \ Then login fails as expected. After I remove the "\" character from userid it logins in.
  4. Some users are reporting that by manually specifying the server address in the configuration as
  5. This one is listed as a fix for Communicator in the comments of , but it seems reasonable to be applicable to Lync also. Office 2011 Outlook not configured to use Exchange, but the Communicator of Mac option the calender/presence integration is enabled. Unchecking such integration resolved by problem. If you have difficulty even to go to the option page, try to set the Communicator's preference "DisableCalendarPresence" to 1



October 12, 13 and 20 – Adding workarounds and reordering with most likely listed first

October 20 – Changing subject as this is not specific to Office 365 but also with on-premise installations.