A computer-implemented method comprising: receiving, by one or more computing systems of a message processing system (110, 640), configuration information from a user regarding messages intended for clients of a first messaging platform (150, 212, 232), wherein the configuration information includes a list of predefined message categories to be used for messages intended for the client devices of the first messaging platform (150, 212, 232), wherein the configuration information specifies multiple categories of spam messages; storing, by one or more computing systems, the configuration information for later use; receiving, by the one or more computing systems and from one or more second messaging platforms (150, 210, 230), a plurality of messages originating from computing devices associated with the one or more second messaging platforms (150, 210, 230), each message having one or more message characteristics and an intended destination computing device that is associated with the first messaging platform (150, 210, 230); analyzing, by the one or more computing systems and for each of the plurality of messages, the one or more message characteristics; identifying, by the one or more computing systems and based at least in part on the analyzing, one or more sets of messages from the plurality of messages; for each identified set of the identified one or more sets of messages, determining, by the one or more computing systems and based at least in part on the configuration information received from the user, one or more message categories associated with the identified set of messages; processing, by the one or more computing systems, at least one of the identified one or more sets of messages in accordance with the one or more determined message categories and the configuration information, wherein processing the at least one identified set of messages includes providing the at least one identified set of messages to the first messaging platform (150, 210, 230) with an indication of the one or more determined message categories for the at least one identified set of messages. receiving, by one or more computing systems of a message processing system (110, 640), configuration information from a user regarding messages intended for clients of a first messaging platform (150, 212, 232), wherein the configuration information includes a list of predefined message categories to be used for messages intended for the client devices of the first messaging platform (150, 212, 232), wherein the configuration information specifies multiple categories of spam messages; storing, by one or more computing systems, the configuration information for later use; receiving, by the one or more computing systems and from one or more second messaging platforms (150, 210, 230), a plurality of messages originating from computing devices associated with the one or more second messaging platforms (150, 210, 230), each message having one or more message characteristics and an intended destination computing device that is associated with the first messaging platform (150, 210, 230); analyzing, by the one or more computing systems and for each of the plurality of messages, the one or more message characteristics; identifying, by the one or more computing systems and based at least in part on the analyzing, one or more sets of messages from the plurality of messages; for each identified set of the identified one or more sets of messages, determining, by the one or more computing systems and based at least in part on the configuration information received from the user, one or more message categories associated with the identified set of messages; processing, by the one or more computing systems, at least one of the identified one or more sets of messages in accordance with the one or more determined message categories and the configuration information, wherein processing the at least one identified set of messages includes providing the at least one identified set of messages to the first messaging platform (150, 210, 230) with an indication of the one or more determined message categories for the at least one identified set of messages.