Recent policy mechanisms (notably MTA-STS and DANE) allow email recipient domains to advertise their support for TLS email transport. REQUIRETLS (RFC 8689) complements those mechanisms by giving message senders the ability to send messages with the requirement that they be transported over TLS -- or not at all. This talk describes the REQUIRETLS protocol extensions as well as potential mechanisms to allow users to control the selection of the REQUIRETLS mechanisms for relevant messages.