Honestly, I can't understand why this site is listed as malicious. Tried out out and it worked just fine. Its fun sending letters to the future.
I wouldn't exactly put my credit card in it, but it seems trustworthy enough to be worth a shot.
Visiting this site may lead to negative visitor experience due to the past actions of the owners of this site which may include: distribution of malware, drive by viral downloads, or spamming.