A method for determining relevance of messages in group messaging services, the method comprising: - receiving by a Messaging Server a message from a sender user which belongs to a group of messaging service; - storing a copy of the message in a Communication Archive communicated with the Messaging Server; - requesting by the Messaging Server from a group management server a list of users (A, B, C) which belong to the group of the sender user, each user of the list (A, B, C) being associated with a presence status selected from online and offline; - for each user of the list (B, C) except the sender user, the Messaging Server requesting to deliver (7, 9) the copy of the message; the method being characterized by further comprising: - receiving by the Messaging Server, from at least one of the users of the list (A, B, C), a signalling with an indication of relevance of the message; - delivering, by the Messaging Server to every user (A, B, C) of the group whose presence status is online, the indications of relevance signalled for the message and information to identify the message, the information to identify the message comprising an identifier of the group and a first identifier of the message sent from the Messaging Server to the sender user device; - displaying the message in the devices of users (A, B, C) formatted according to the indications of relevance. - receiving by a Messaging Server a message from a sender user which belongs to a group of messaging service; - storing a copy of the message in a Communication Archive communicated with the Messaging Server; - requesting by the Messaging Server from a group management server a list of users (A, B, C) which belong to the group of the sender user, each user of the list (A, B, C) being associated with a presence status selected from online and offline; - for each user of the list (B, C) except the sender user, the Messaging Server requesting to deliver (7, 9) the copy of the message; the method being characterized by further comprising: - receiving by the Messaging Server, from at least one of the users of the list (A, B, C), a signalling with an indication of relevance of the message; - delivering, by the Messaging Server to every user (A, B, C) of the group whose presence status is online, the indications of relevance signalled for the message and information to identify the message, the information to identify the message comprising an identifier of the group and a first identifier of the message sent from the Messaging Server to the sender user device; - displaying the message in the devices of users (A, B, C) formatted according to the indications of relevance. - receiving by the Messaging Server, from at least one of the users of the list (A, B, C), a signalling with an indication of relevance of the message; - delivering, by the Messaging Server to every user (A, B, C) of the group whose presence status is online, the indications of relevance signalled for the message and information to identify the message, the information to identify the message comprising an identifier of the group and a first identifier of the message sent from the Messaging Server to the sender user device; - displaying the message in the devices of users (A, B, C) formatted according to the indications of relevance.