GAS adding a non domain member to google group doesnt work - google-apps-script

Question

I'd like to create a spreadsheet to let user create his own google groups for mailing list purpose.
I can add domain's member to grups with this code:
function addGroupMember (groupEmail, userEmail,ruolo) {
var member = {
email: userEmail,
role: ruolo
};
try {
member = AdminDirectory.Members.insert(member, groupEmail);
Logger.log('User %s added as a member of group %s.', userEmail, groupEmail);
}catch(e){
Logger.log("adding in:" + groupEmail + " failed user email: "+ userEmail + " role: " + ruolo + " error:" + e);
}
But if i try to add a non domain's user (i can do it in group management) it fails with this error:
[16-08-12 14:54:13:113 CEST] adding in: mygropu#mydomain.it failed user e mail: user#otherdomanin.it role: MEMBER error: Exception: Invalid Input: memberKey

Answer 1

As the error log shows exception Invalid Input: memberKey, it means that you may not able to give the real memberKey/ authentic memberKey. memberKey is the user's or group priary email address, user's alias email address or the user's unique id
To get the memberKey, you can use the Members:get to retrieves a group members properties.
HTTP request:
GET https://www.googleapis.com/admin/directory/v1/groups/groupKey/members/memberKey
Response:
{
"kind": "admin#directory#member",
"etag": etag,
"id": string,
"email": string,
"role": string,
"type": string
}
id is the unique ID of the group member. A member id can be used as a member request URI's memberKEy

Answer 2

I made some test more, and found the clue!
The Exception: "Resource Not Found: email#otherdomain.com" rises up when the otherdomain is gmail.com and the mail address does not exist.
Using any other domain works even for non existent addresses! I think that G.A.S. checks only for his own domain addresses, but can't do it for other domains.