1. A computer system, comprising: one or more processors; and one or more hardware storage devices having stored thereon computer-executable instructions that are executable by the one or more processors and that configure the computer system to responsively filter electronic messages of a messaging campaign in a multi-tenant environment, including computer-executable instructions that configure the computer system to perform at least the following: maintain tenant-level filtering criteria for each of a plurality of tenants in a multi-tenant environment including, for each tenant: identifying one or more feedback signals from one or more users within the tenant regarding a messaging campaign; and updating tenant-level filtering criteria for the tenant with respect to the messaging campaign, including: when the messaging campaign has not yet been categorized, and when the one or more feedback signals indicate that the messaging campaign is undesirable to the tenant, updating the tenant-level filtering criteria to signal the messaging campaign as undesirable for the tenant; or when the messaging campaign has previously been categorized as undesirable, and when the one or more feedback signals indicate that the messaging campaign is desirable to the tenant, updating the tenant-level filtering criteria to signal the messaging campaign as desirable for the tenant; calculate a reputation score for each of the plurality of tenants; based on a threshold number of tenants, which each have a threshold reputation score, reaching a consensus that the messaging campaign is undesirable, update global filtering criteria to signal the messaging campaign as being undesirable according to the consensus; and based on updating the global filtering criteria to signal the messaging campaign as being undesirable according to the consensus, filter a particular electronic message that is identified as being part of the messaging campaign, including blocking the particular electronic message from being delivered to a computer system associated with at least one tenant.