If I may offer a minor suggestion. It would be an added benefit to restrict one user group from sending messages to specific user group(s). In other words, admin or even moderator can send to members but not guests. This may be an option already as I am only about a half hour familiar with this product. If not, I think it would cut down on the chance of staff members being in a rush and sending messages to guests which may inadvertently deter new registration eg., a message addressing technical or member issues.