A group messaging system enabling anonymous collective communications in a group which is locally defined in association with a group owner's messaging account, wherein messaging software at the group owner converts a group message into multiple one-to-one group messages destined to each group member in collaboration with the said group membership resolution process. The invention further includes a group message reply process wherein the messaging software at a recipient's side composes a reply message and transmits it to the group owner messaging software which then forwards it to the group members in collaboration with said group membership resolution process, thereby providing a means of designating the identity of a group in the group owner messaging account, sending a group message, and hiding the identities of individual recipients during the lifetime of the group message. The group owner side can additionally perform access control for group communications.