A method is provided for inserting signature blocks into a message being transmitted along a communication path between a first client station and a second client station. The method includes a step of receiving, at an intermediate node in the communication path, a message transmitted from the first client station destined for delivery to the second client station. The message bears a sender-identifier (e.g., email address) and a recipient-identifier (e.g., email address). The method further includes a step of selecting, based at least in part on the sender-identifier, a predefined signature block for the message. The method further includes a step of inserting the selected signature block into the message. The signature block to be inserted may be based on both the sender identifier and the recipient identifier.