Communication is the exchange of thoughts, messages, or information, as by speech, visuals, signals, writing, or behavior.  As such communication requires a sender, a message, and a recipient, although the receiver does need not be present or aware of the sender's intent to communicate at the time of communication and therefore communication can occur across wide ranges of distances in both time and space.  Typically communication requires that the communicating parties share an area of communicative commonality and a communication process is typically considered complete once the receiver has understood the message of the sender. 
The first major model of communication, see Shannon et al in “The Mathematical Theory of Communication” (University of Illinois Press, 1949) consisted of three primary parts, namely sender, channel, and receiver.  In a simple model, often referred to as the transmission model or standard view of communication, information or content (e.g. a message in a natural language) is sent in some form (e.g. as spoken language) from a source/sender/encoder to a destination/receiver/decoder.  This common conception of communication simply views communication as a means of sending and receiving information and according to Shannon is based on the following elements:                an information source, which produces a message;        a transmitter, which encodes the message into signals;        a channel, to which signals are adapted for transmission;        a receiver, which decodes (reconstructs) the message from the signal; and        a destination, where the message arrives.         
This model was expanded by Berlo et al into the Sender-Message-Channel-Receiver (SMCR) Model of Communication, see for example “The Process of Communication” (Rinehart & Winston Press, New York, 1960) which separated the communication model into clear parts and has been expanded upon by other scholars.  Accordingly, such models allow one-way, two-way, and multi-way conversations to be modeled, analysed and implemented within telecommunications infrastructure across multiple communications technologies to perform the transmitter, channel, and receiver such as wireless, wired, and fiber optic.  Such models also support multiple communication formats including, for example, voice, either through Plain Old Telephone Service (POTS) or Voice-over-Internet Protocol (VOIP), as a general two-way communication process, electronic mail, commonly referred to as email and generalized into one-way communications, and Short Message Service, commonly referred to as SMS or text and similarly generalized into a one-way communication.  Accordingly, communications common today such as “Tweeting” on the social media network Twitter™ and concepts such as “email threads” and Instant Messaging are merely concatenations of multiple discrete email and SMS one-way communications. “ Tweeting” and email provide multicast communications wherein the message is communicated to a plurality of recipients simultaneously in a single transmission from the source wherein copies of the message are automatically created in other network elements, such as routers, but only when the topology of the network requires it. 
However, these models and the consideration of the interactions between sender and recipient is that the message is sent by the sender and received by the recipient as a single process and that other aspects of the communications channel such as voicemail, email server, and text server that store the senders message prior to the recipients receipt are modeled as a delay within the communications channel.  However, going back to the primary definition of communication is the exchange of thoughts, messages, or information and accordingly these models and their physical implementations do not provide for verification that the exchange has occurred in the manner the sender intended unless for example the voice communication is a two-way session or a subsequent one-way communication from the recipient referencing the original one-way communication or its content is received by the sender. 
According, whilst voicemail's introduction enabled people to leave lengthy, secure and detailed messages in natural voice, working hand-in-hand with corporate and personal phone systems it also broke the two-way communication session methodology of telephony prior to its introduction.  This is further compounded by there being two main modes of voicemail operation, namely telephone answering and voice messaging.  Telephone answering voicemail answers outside calls and takes a message from any outside caller, either because the extension was busy or rang with no-answer, or voice messaging which enables any subscriber with a mailbox number to send messages directly to any or many subscribers' mailboxes without first calling them.  Accordingly, the sender is unable to determine whether the recipient has listened to the message, deleted it unheard, or stopped listening part way through the voicemail.  With the rapid uptake of portable electronic devices (PEDs) many individuals now have three or more telephone numbers, for example home, cellphone, and work, thereby increasing the complexity of ensuring a message is delivered to a recipient, yet alone played and understood. 
These issues have continued into email and SMS/text communications in the last thirty years as these systems have proliferated.  With the adoption of email into business activities and its replacement of physical mail delivery which provided options for delivery verification such as from the mail delivery organization itself or through a signature of the recipient the absence of verification presented an issue.  Accordingly, some email systems such as Microsoft™ Outlook introduced email to provide a digitally time-stamped record to reveal the exact time and date that an email was received and/or opened according to the settings established by the sender.  However, due to the nature of the technology, email tracking cannot be considered an absolutely accurate indicator that a message was opened or read by the recipient.  Even receiving a reply referencing the original email does not address whether the recipient read the content. 
Likewise within SMS/text systems the vast majority of such systems, commonly referred to as Instant Messaging (IM) systems, present the same issues of whether the recipient received and read the text message.  Accordingly, in these systems the receipt of a reply from the recipient may provide some indication that they received or read the message but their reply could be a coincidence.  One notable exception to this is Research in Motion's Blackberry™ Messenger service which provides a delivery notification on the sender's messaging interface and a read notification when the recipient opens the message.  However, this service is feasible as the entire messaging system is routed through Research in Motion's own messaging servers. 
In many instances the sender whilst wishing to send the recipient a message does not wish to send the message at the time they decide to do so as they do not wish to disturb the recipient or potentially disturb the recipient.  For example, the sender may need to send a message to the recipient at 10 pm in the evening at their home but does not want to disturb the recipient and their family at home.  Accordingly, the sender may decide not to send the message at that time and to do so in the morning wherein they may forget or miss the recipient.  Alternatively they may elect to use another form of communications, such as email, which is not delivered to the recipient due to a network issue or is not seen or opened by the recipient. 
Accordingly it would be beneficial to provide enhancements to voicemail, email, SMS and other communications that provide additional information to the sender with respect to the delivery to and recovery by the recipient of the message such that not only do they have the option to elect to receive a delivery notification in communications systems that today do not provide such information, but that in these systems and those supporting delivery notifications increased information is provided to the user allowing them to ascertain or estimate the recipient's absorption/reading of the message. 
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.