The present invention relates to a method for blocking undesirable messages (MMs), which includes the following steps: a message is sent from a sender (MMS UA A) to a transmitter (MMS R/S A); the message is sent from the transmitter (MMS R/S A) to a service (MMSE SP B); the message is transmitted from the service (MMSE SP B) to a recipient (MMS UA B), such recipient being serviced by the service provider. The message is transmitted from the service provider only if the sender does not figure on a list of exclusions. Preferably, the list of exclusions is managed by the service.