We are just starting to explore our trial of the Helpdesk and have run into a curiosity.  We use Skype for Business as our Corporate phone system.  It is set up to send us a transcribed email when someone leaves us a voicemail.  I set up our "Helpdesk" user with a phone number and license so a user can call Helpdesk, leave a voicemail, and the voicemail triggers an email to our Helpdesk email address.  This successfully opens a ticket.  It is outstanding!  BUT, when a user calls from a cell phone or non company phone and leaves a voicemail the transcribed email goes right to the Helpdesk_ignore mailbox.  A ticket never gets created.
Would anyone know why a voicemail from a company phone creates a ticket but a voicemail from an outside caller does not?  Any suggestions on how to fix this?