Adobe Acrobat DC has stopped working - resolving e-mail addresses

I am attempting to create a Survey PDF and Distribute it using the distribute option within Acrobat DC.

Here's the steps I have been using:

1. Create form
2. Click "Distribute"
3. Select "Send using Adobe Acrobat DC"
4. Select "To" to acquire email addresses
5. Select "Send"
6. Dialog box appears "Resolving e-mail addresses", bar fills approximately 50% green, then
7. Dialog box appears "Adobe Acrobat DC has stopped working", program closes.

I am using the program within a private network, accessing ONLY internal email addresses which are all on my internal email server.
I do NOT wish to access the outside world with this Survey.  It is intended to be used completely on my side of our firewall.

Within Acrobat I have set my Network preferences to LAN but no JOY!

Is this feature non-functional, or have I missed a setting?

Any help would be appreciated.  I'd much rather not send it via e-mail attachment and process the results manually via email.