There are several websites that let you send an email to yourself in the future (example). It's also possible to accomplish something similar in a lower-tech way, like making a time capsule.
Are you allowed to tell lashon hara to yourself? In particular, if someone did something bad that you'll probably forget in 50 years, are you allowed to remind yourself of it using one of these websites?
I'm assuming a situation where לא תקם ולא תטר doesn't apply. You're reminding yourself for a valid reason, but not necessarily complying with all the conditions listed by the Chafetz Chaim.
An example would be a case where someone 50 years older than you did something that older people might be prone to. You're afraid that in 50 years, when you're that age, you might end up doing the same thing, so you send an email to remind yourself not to. Do you have to follow the 7 conditions? For instance, can you exaggerate a little if you think that will be more persuasive to your 50-years-older self?