Google's Directory API incorrectly adding personal gmail address to groups

[Farooq Sadiq]

Google's Directory API incorrectly adding personal gmail address to a google group when I use the api to insert a non-gmail addresses. This only happens for a subset of addresses for several domains @indiana.edu, @arizona.edu... (I assume it is connected to the organizations own use of GoogleApps). 

I can reproduce the issue using the Google-Api-Explorer, without any code.  I noticed the issue using google-api-php-client.

Example :

       $gData = $this->service->members->insert($groupEmail,$gMember);

I have filed a ticket with Google. Has anyone encountered this issue, or can you shed light into how a personal gmail account is linked to an @organizatio.edu account in GoogleApps.