Composing, forwarding, and rendering email system

A computer implemented method for generating a signature header in a draft source email, the method comprising:

• receiving a command to add an indexed signature to a draft source email;
• adding an indexed signature to the draft source email, wherein the indexed signature comprises an email address having signature locator preface;
• adding a signature header in a header of the email to the draft source email, wherein the indexed signature includes a first instance of the signature key and the signature header includes a second instance of the signature key and the first instance of the signature key matches the second instance of the signature key;
• and
• transmitting the draft source email as a source email, wherein the second instance of the signature key is unmatched among signature keys within the signature header.

A computer implemented method for communicating a signature, the method comprising:

• receiving a source email from a source client, the source email comprising a signature index entry and a text body part;
• determining 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;
• and
• responsive to a determination that the destination client is capable of rendering the signature index entry, forwarding the source email to the first recipient as a delivered email using the text body part of the source email such that an indexed signature is present in the text body part of the delivered email and the indexed signature is an email address having signature locator preface.