Hi,
Did the Lync Server and the Exchange in the same forest?
Usually, there is no special configuration for basic integration if Lync Server and Exchange in the dame forest.
Please also test the issue using a Windows OS computer, and check if the issue still happen.
If the issue not happen for Windows OS system, it can be the local client issue for Mac computer.
If the issue still happen for Windows OS System, please press Ctrl and right click Lync icon in the taskbar, open configuration information. On the open page check if EWS status and MAPI status are OK. If the EWS status not shows OK, please double check
the EWS and autodiscover configuration for Exchange, and then test the issue again.
Best Regards,
Eason Huang