It is possible for users of R5 clients to set their own email address in their location document. With default settings on the server this is also the email address which is communicated to the internet recipient.
Of course you would not want your users to pose as the CEO of your company in communication internally or externally. Suppose someone sends a mail as the CEO telling you, you are fired! As a joke, this might not be welcomed. It is possible to lock out the communication of the internet address in the location document en overruling it with the one the admin assigns in the Domino Directory.
Do as follows in the Configuration document of you SMTP server(s):
Edit the configuration document. Go to the tab MIME - Advanced - Advanced - Advanced Outbound Message Options. in the field : Notes fields to be removed from headers = INetFrom. This removes the internet address that was set in the location document. Than go to the Tab : MIME - Conversion options - Outbound and 'Enable' the internet address lookup. This will ensure that the internet address that you specified in the person document in the Domino Directory will get transmitted. I would als recommend that one sets the Advanced Outbound message Option : RFC822 Phrase handling to the Common Name as this is usefull for the recipient to have a name already filled in when adding the address to the personal addressbook of the recipients mailclient.