I particularly like that FutureMe is a service solely dedicated to the task of sending an email in 1/3/5 years. I'm guessing infra-costs are pretty low - the site hasn't changed much in 15 years i.e. I would hope they can continue running long into the future, whereas some of these other services are at the whims (gmail excluded) of survival against a multitude of competing services and being able to continue running long into the future. A lot changes in 5 years - it feels like a lot of services from 15 years ago don't even exist anymore. Oh and a nice bonus for some people - you can allow your emails to be shown publicly (and anonymously ;)