I remember visiting this website once...
It was called Mail2Tor@onion
Here's some stuff I remembered seeing:
Mail2Tor is a free anonymous e-mail service to protect your privacy. It allows anyone to send and receive email anonymously via webmail or with an email client. You will need to have Tor browser installed on your computer to access Mail2Tor (mail2tor2zyjdctd.onion).
For help...contact admin@Mail2Tor.com. Change your password by yourself. Deactivate your account by yourself too. All messages are stored in encrypted form. In the headers of your emails will not appear your IP number.We will add more servers soon. All problems kindly reported by users will be solved. Be patient, please.
We have been receiving a number of emails regarding forgotten/invalid password. Do note that by virtue of the setup we are unable to verify your identity and hence unable to aid in this matter. Do try not to forget your password. We will not allow reset/hijack of accounts for the privacy and safety of all.
5th July 2017 - Server was dead due to hard disk failure. All in and out mails were stuck as unable to route. Had to reconfigure every shit. Donations appreciated.
Our front end server got seized by the Swedish Police. Please wait while we find alternative solutions.
127.0.0.1 - - [30/May/2016:08:51:31 +0000] "GET /SEND-8-BTC-TO-1LCf3AVSdxWCurVmFUA1Rb9Lxo6gLEoZdw HTTP/1.1" 400 0 "-" "Mozilla/5.0 (Windows NT 6.1; rv:31.0) Gecko/20100101 Firefox/31.0"