Adding external mail contacts to a distribution group seems to randomly add the user instead of the mail contact

Question

I've added a external mail contact for all my mailbox users because all the users have other jobs and other external email addresses.  Since these users don't normally log on to my domain to get email, I need to create a distribution list with all their
external email addresses.  I've scripted the creation of all the external mail contacts, from the mailbox users and I use AD's Notes field to contain the users external address. When using add-DistributionGroupMember and supplying the external mail
contact email address as the "-Member" param, about half of the time the users mailbox user gets added to the group instead of the external contact.  I don't see any arguments to tell add-DistributionGroupMember to use only mail contacts.
1) I don't even know how it's finding the mailbox user because I'm supplying an external email address which is only in the external mail contact.
2) Some members of the group are correctly added as external contacts, some are mailbox users.
3) I only want the external mail contacts in the group
If it helps, here's the line that I use to add members to the group. I've tried mail enabling the mail contacts, no help...
Add-DistributionGroupMember–identity“AltEveryone”–member(get-QADuser$_.Name).Notes 
Thanks for any help.

Answer 1

You should ask questions like this in the Exchange forum.  It is not a scripting question but is a product behavior question.
You cannot add an external contact without first creating the contact first.
¯\_(ツ)_/¯