Electronic mail system with functionality to include both private and public messages in a communication

A computer-implemented method of providing different versions of an e-mail message to different recipients, the method comprising:

• receiving an e-mail message composed by a sender on a sender computing device, said e-mail message being addressed to at least a first recipient and a second recipient, wherein the e-mail message includes a non-private text message portion that is not private to any particular recipient, and includes a private text message portion that is private to the first recipient, and where the e-mail message has a sender-specified policy regarding tracking of metadata;
• securely transferring the e-mail message to a server system, and storing the e-mail message on the server system such that both the non-private and private text message portions are stored in association with a common message identifier;
• sending a first notification message including a first message key to the first recipient at a first recipient e-mail client;
• sending a second notification message including a second message key to the second recipient at a second recipient e-mail client;
• receiving and authenticating a first recipient e-mail address and the first message key from the first recipient e-mail client;
• providing the first recipient e-mail client access to retrieve the non-private text message portion and the private text message portion of the e-mail message from the server system via a secure HTTPS communications protocol responsive to the authenticating of the first e-mail address and the first message key;
• receiving and authenticating a second e-mail address and the second message key from the second recipient e-mail client;
• if the sender-specified policy enables e-mail message tracking for the second recipient e-mail client, sending e-mail message tracking metadata to the second recipient e-mail client indicating retrieval of the e-mail message by the first recipient;
• and
• providing the second recipient e-mail client restricted access to retrieve the non-private text message portion responsive to the authenticating of the second e-mail address and the second message key.