Can non-members subscribe to a public group?

[bart_vermeersch]

We got a servicedesk call from a group owner that his mail to the group was received by a colleague who is not a member of that group. The group was public by mistake, so we changed it to private (it would be nice if admins can change this without having to add themselves as owner first).

However, can a user subscribe to receive emails from a public group while not being listed as a member of that public group?

Thanks!

[#2 · Accepted solution]

AFAIK, no.

Everyone can join a public Group, but only members can subscribe.

[#3]

I believe Salvatore is correct!

[#4]

Thanks!

Any idea how a non-member could receive a mail sent to a group and/or how to troubleshoot?

[#5]

Could it be that he/she at some point joined the public group (thus receiving the email) and subsequently abandoned the group or was removed?

Just an idea...

[#6]

BTW, admins can change the privacy setting with PowerShell without making themselves an owner.

[PS] C:\> Set-UnifiedGroup -Id GroupXX -AccessType Private

A user will only receive notifications from a group if they are in the subscriber list for the group. To check this, run:

[PS] C:\> Get-UnifiedGroupLinks -Id GroupXX -LinkType Subscriber

[#7]

Thanks. We wanted to check the mail headers but the user was unable to find the messages back after we've changed the group to private.

We think she looked in the public group assuming it was part of her own mailbox. Supporting some users can be rather challenging. 

[#8]

"some users" - maybe "all users"?

[#9]

@Salvatore Biscari  I see that anyone can add members to the Public Group even without being a member or owner of the Public Group is there a way to limit this?