There is a 'check names' feature in Outlook which compares the name(s) of email recipients in the 'To' field of a new email to your Outlook Contacts. For example, if you type "Joe" in the 'To' field of a new email, and click send, Outlook will do a 'check names' and suggest which "Joe" you would like the email to go to, based upon what is in your Outlook contacts.
We have seen an issue where Outlook will freeze and crash on this process when ndMail is enabled.
Upgrade Exchange Server to 2016 or Exchange 365
Currently, we have only see this issue occur where Exchange 2010 is being used. To correct this issue, upgrade your instance of exchange to Exchange 2016 or Exchange 365. You may need to contact your IT or mail administrator to accomplish this.