To avoid ex-employees, or external senders, addressing to groups from a personal email account to your entire company through use of a "common" group name, i.e., All_Employees@CoName.com, do the following:
1. Create a Mixed Use group and add all domain servers to the group with the exception of the Internet mail server. Additionally, add the "All Employees" group to the new mixed use group.
2. Open the Groups view of the administration server's address book and select the "All Employees" group by right-clicking to display the Document Properties.
3. Select the document's "Security" tab and deselect "All readers and above". Select all the appropriate user names that require access and add the newly created mixed use group to the selected list.
4. Replicate the address book to the SMTP server and verify that it no longer has the "All Employees" document in the groups view.
This disallows the use of the group in mailing from outside the Notes system since the Internet, SMTP, mail server will not see the document to use for addressing.