I think you should give instructions on how to send mail without your site anyway, if someone doesn't want you to read his message (knowing that it still will be read by the prison staff).
Kudos on your initiative: you might want to get in touch with the freejeremy.net staff, for one, that could be interested in using your project.
This is a well-intentioned project, but the misleading title and vague About section really puts me off. This is not an app/site that makes it easier to send something to "a loved one", it makes it easier to send something to your loved one.
Which is fine, except the site itself remains opaque about how it works or what it does. Are people really supposed to just start entering in things after the "Dear Blake..." prompt and hit send? There's a prominent "About" link, but it's not great UI/UX to force users to navigate your site just to figure out what the purpose of it is. The cynical person in me thinks this is an attempt to astroturf the justice system, so that supporters of Mr. Benthall can tout a media-friendly number of how many people have written on his behalf.
But the cynical UI designer in me thinks that what will happen is that a bunch of "test/asdfjkljks" messages will be sent off to the site's maintainer, who will either just forward them to the prison or be overwhelmed with trying to filter signal from noise...and both scenarios do not seem very beneficial to Mr. Benthall.
I don't want to judge intentions by quality/style of writing, but the About section is not very appealing to me. Telling me that Blake "led a very normal life and was extremely kind, generous, and always willing to help" just screams of an attempted saccharine whitewash. So I looked up what Mr. Benthall is alleged to have done...and really, the allegations aren't particularly ugly for him (e.g. he isn't yet accused of hiring to kill someone). The About section should not be coy about the allegations, it smacks of dishonesty and is an insult to the audience.
However, I do applaud that the OP looked at the letter-sending process itself and found it to be "obtuse". There probably is a need to reduce the friction here, and I would encourage the OP to also write about the steps involved...as it is, just calling it "obtuse" doesn't really generate much sympathy.
There was a great NYT article about "The Cellblocks' Amazon.com"...a startup that navigated the bureaucratic roadblocks of sending gift packages to prisoners...this is what I thought the OP was trying at: http://www.nytimes.com/2013/11/03/nyregion/sendapackage-bill...
edit: My comment is more harsh than I'm probably feeling... I have no opinion of Mr. Benthall currently, I'm just pointing out that the site's vagueness doesn't really do him favors. If he's being harshly punished by an overreaching justice system, more details/transparency about it is better for generating sympathy. And again, kudos to the OP for trying to navigate the prison-communication system... a writeup of what that involves would also generate some goodwill toward Mr. Benthall (as well as expanding awareness of our justice system in general)
If the concept works well, I'm considering making the recipient user-definable and running it as a non-profit to help people connect with their loved ones who are behind bars. If spam/test messages become a large problem, I will add some preventative measures. In the meanwhile, nothing gets sent without my seal of approval.
For now I just wanted to get something up and running that made it as easy as possible for our friends to reach out to Blake. A number of them have already thanked me because they didn't know how to contact him.
