The present invention provides a computer implemented method for communicating a signature in a received email. Initially, a server receives a source email from a source client, the source email comprising a signature index entry, and a body. The server determines for a first recipient that a first associated destination client is capable of rendering a signature of the signature index entry in response to a selection of an indexed signature. The server, responsive to a determination that the destination client is capable of rendering the signature index entry, forwards the source email to the first recipient as a delivered email using the body of the source email such that an indexed signature is present in the body of the delivered email. In addition, a method for generating a signature header is shown that provides a many to one correspondence between indexed signatures and a signature index entry.