Determining failed delivery of email messages using email notifications

1. A method of ascertaining whether an electronic mail application has not received an electronic mail message, the method comprising acts of:

sending, to a notification service, a request to receive electronic mail notifications, the request sent by a user device of a recipient user that is an intended recipient of the electronic mail message, each electronic mail notification being separate from a corresponding electronic mail message and indicating that the corresponding electronic mail message has been sent to the recipient user;

receiving, by the user device of the recipient user, at least one notification retrieved from a notification list of the notification service, the at least one notification indicating that a first electronic mail message has been sent to the recipient user;

determining, by the user device of the recipient user, whether the first electronic mail message indicated by the at least one notification has not been received by the electronic mail application of the user device of the recipient user by comparing the at least one notification to an email list of electronic mail messages received by the user device of the recipient user, thereby determining failed delivery of the first electronic mail message;

determining, by the user device of the recipient user, an elapsed time since the first electronic mail message was sent, based on a time stamp included in the at least one notification, the elapsed time being indicative of whether the first electronic mail message was lost or was delayed; and

in response to the user device of the recipient user determining that the first electronic mail message was not received, the user device of the recipient user notifying a sender of the first electronic mail message that the first electronic mail message was not received.

2. The method of claim 1 , wherein the notification list resides on a network device separate from the user device.

3. The method of claim 1 , wherein the notification list comprises a hash table including the at least one notification, and wherein the at least one notification comprises a hash indicative of the first electronic mail message.

4. The method of claim 1 , wherein the notification list comprises a hash table including the at least one notification, the at least one notification comprising a first hash indicative of the first electronic mail message, and wherein the act of determining whether the first electronic mail message has not been received further comprises:

comparing the first hash to a hash of each electronic mail message listed in the email list until a match is found or an end of the list is reached.

5. The method of claim 1 , further comprising:

sending, by the user device of the recipient user, user credentials to authenticate the recipient user.

6. The method of claim 1 , further comprising an act of:

registering the recipient user with a registration service to receive electronic mail notifications.

7. A computer-readable storage device encoded with computer-executable instructions that, when executed by at least one processor, perform a method of ascertaining whether an electronic mail application has not received an electronic mail message, the method comprising acts of:

sending, to a notification service, a request to receive electronic mail notifications, the request sent by a user device of a recipient user that is an intended recipient of the electronic mail message, each electronic mail notification being separate from a corresponding electronic mail message and indicating that the corresponding electronic mail message has been sent to the recipient user;

receiving at least one notification retrieved from a notification list of the notification service, the at least one notification indicating that a first electronic mail message has been sent to the recipient user;

determining whether the first electronic mail message indicated by the at least one notification has not been received by the electronic mail application of the user device of the recipient user by comparing the at least one notification to an email list of electronic mail messages received by the user device of the recipient user, thereby determining failed delivery of the first electronic mail message;

determining, by the user device of the recipient user, an elapsed time since the first electronic mail message was sent, based on a time stamp included in the at least one notification, the elapsed time being indicative of whether the first electronic mail message was lost or was delayed; and

in response to the user device of the recipient user determining that the first electronic mail message was not received, the user device of the recipient user notifying a sender of the first electronic mail message that the first electronic mail message was not received.

8. The computer-readable storage device of claim 7 , wherein the notification list resides on a network device separate from the user device.

9. The computer-readable storage device of claim 7 , wherein the notification list comprises a hash table including the at least one notification, and wherein the at least one notification comprises a hash indicative of the first electronic mail message.

10. A system for controlling access to a notification list including a plurality of notifications for a plurality of users, each notification indicative of an electronic mail message sent to a particular user, the system comprising:

at least one processor programmed to:

receive a request for notifications, the request sent by a user device of a recipient user that is an intended recipient of the electronic mail message, each electronic mail notification being separate from a corresponding electronic mail message and indicating that the corresponding electronic mail message has been sent to the recipient user;

in response to receiving the request, determine one or more notifications in the notification list that correspond to the recipient user; and

in response to determining one or more notifications in the notification list that correspond to the recipient user, send the one or more notifications to the user device of the recipient user to enable the user device to determine failed delivery of the electronic mail message by comparing the one or more notifications to an email list of electronic mail messages received by the user device of the recipient user, to determine an elapsed time since the electronic mail message was sent, based on a time stamp included in each of the one or more notifications, the elapsed time being indicative of whether the electronic mail message was lost or was delayed, and, in response to the user device of the recipient user determining that the electronic mail message was not received, to notify a sender of the electronic mail message that the electronic mail message was not received.

11. The system of claim 10 , wherein:

the notification list comprises a hash table including the one or more notifications;

the one or more notifications comprise a hash indicative of a first electronic mail message sent to the recipient user; and

the at least one processor is further programmed to access the hash table.

12. The system of claim 10 , wherein the request for notifications includes user credentials, and

wherein, upon receiving the request for notifications, the at least one processor is further programmed to initiate an authentication of the recipient user using the user credentials.

13. The system of claim 12 , wherein the at least one processor is further programmed to initiate the authentication by sending a verification request to a registration server to verify an identity of the recipient user.

14. The system of claim 10 , wherein the at least one processor is further programmed to:

receive at least one notification from an originating sender of an electronic mail message indicating that the electronic mail message has been sent to the recipient user; and

store the at least one notification in the notification list.