a method and system for preventing recipients from being added and / or removed from a message thread in an e - mail and / or calendaring application . recipients of a thread message may be allowed to seek and obtain permission from a thread originator to insert a recipient to and / or remove a recipient from the thread . the originating user of a message thread can prevent insertion and / or removal of recipients in an e - mail message thread and / or a calendaring system invitation message by selecting from corresponding message composition user interface options . a mechanism persistently registers the recipient removal and / or insertion settings provided by the originating user , for example as settings stored in and conveyed with the messages themselves . the originating user can permit non - originating users to insert and / or remove recipients from the thread . the originating user can select an option in the message composition user interface that requires and / or allows non - originating users to request permission to insert and / or remove a recipient to a thread . the permission request is forwarded to the originating user , who can then accept or reject the request . the originating user can also expressly list or otherwise indicate which user cannot be inserted into the message thread , and / or which recipients cannot be removed from the message thread .