Since updating to Mac Outlook 15.17 over the weekend, the Check Names button is no longer available (grayed out) with my IMAP account that searches an LDAP directory for email addresses. I have verified that I am still able to browse this LDAP server using
the Address Book in the ribbon, so this isn't an LDAP communication issue.
This worked as of Friday 12/11 before I installed the most recent updates.
Cross-post from Office 365 Mac community: https://community.office365.com/en-us/f/153/t/423477
Update 2015-01-11:
The Outlook 15.17.1 update did not resolve this issue and it still persists.
Update 2016-05-15:
Mac Outlook 15.22 (160506) still has the same problem. I have submitted an official request to fix this on Mac Outlook UserVoice. Please vote here if you want Check Names functionality restored by MS.
Update 2016-08-01
Mac Outlook 15.25 update did not resolve this issue.
Updated 2017-03-16
Mac Outlook 15.33 (170315), issue still not resolved.
Cross-posted to new forum UserVoice for Outlook for Mac - Business - please vote!
Re-promoting orginal consumer forum UserVoice for Outlook for Mac - please vote!