The volume of outgoing electronic messages from a given entity may be restricted by preventing the messages, such as spam, from being sent. Messages may be restricted, for example, by serializing outgoing messages using a mutual-exclusion locking technique or by using a ticket-based system. Serialization may occur, for example, at a web level in web-based implementations. In one system, a limited-use ticket is generated that allows an entity to send one or more electronic messages, and the ticket is provided to the entity. A request is received from the entity to send an electronic message, and the request is associated with the ticket and the electronic message. After receiving the request, a determination is made as to whether the ticket is valid and, if the ticket is determined to be valid, the electronic message is approved for sending.