Mail in the future

Long time ago, I used a service for online greeting cards and I loved a particular feature; it was the feature to schedule the delivery to a future date. I am not sure if other providers had this feature or not, but they surely didn't make it easy to find; and this made me love this service above all the others. Since then I have wondered how great it would be to able to schedule mails to be delivered in the future. 

Starting from Birthdays and Anniversaries that I couldn't risk forgetting to serious reminders to myself or others, scheduling an email in the future would be a 'desirable' service. Imagine that you are working on a project and would like to personally mail the team each week to request for their progress. Now this would require time, even if you had to send a simple "What's the progress" message each Monday. It would be cumbersome as it would demand you to take out time from the numerous other tasks that you have to do. Won't it be easier, if on one weekend, you fix 4 such mails to be sent in the future on the appropriate dates and set a reminder for yourself to fix more for later (if the project is not over by then). Such a service would save you the effort, while still getting you the response.

Another scenario where such a service seems useful to me is sending the 'last words' of a man to his kin. Very often, certain secrets die with people. Sometimes it is because of the fear or of the want of a better moment, that words just don't come out. In such a scenario, if a person could create a mail to be sent in the future once he/she is dead, to a few chosen recipients. Some wonder, at this point, how could the service know about his/her death ? Well, before the mail is sent (on the specified date by the sender), a confirmation mail could be send to the creator of the mail, giving him some time to react (cancel or reschedule). There are many such possibilities. 

Determined to create such a feature for myself (and use by others), I set out on a domain search. Looking for ideas, I stumbled over 'existing' services that partly fulfill the goals, here are some of them : -

• FutureMe : This service was the first that I had seen (and brought back my childhood ideas about future mails). In terms of a friend , this is like a 'time-capsule'. 
• FutureMail : This service fulfills the 'reminder' aspect of my discussion. It allows one to send himself reminders at any particular time in the future.
• MyLastEmail : This service targets on the final email, mostly in case of death. Although, at the time of writing, the domain seems to have gone dead. 
• LetterMeLater : This service combines most of the features as it allows you to send messages to both yourself and others at any time in the future. One of the attractive features about this is that you don't need to access  the site to create a new message; using this feature, you can send a mail from your own email client to 'me@lettermelater.com' with a few details on the top, and ZOOP, you have scheduled a mail in the future. 
• HitMeLater : As the website boasts, this is like creating a 'snooze' button for yourself; more like reminders.

While these kind of services do solve most of the things that I have in mind, some aspects can't be achieved with one service itself. This motivates me to work on one of my own service to cater my own needs (and that could be used by others as well). 

One of the things mentioned here is note-worthy :-

What if your (or the recipients) email address changes ? 

I believe that this is an acceptable risk. Although, I am convinced that the service provider should facilitate change of 'recipient-address' , 'sending date' or even 'cancellation' of a scheduled mail.

What do you think about such a service ? If I start one, what would be 'your' requirements ?