Understanding the threat model is fundamental: If you don't know what this protects against, it might as well protect against nothing at all; My ISP received my emails in plaintext, so I have to assume that they've got a plaintext backup of those emails.
>How can I trust you?
>You can't. Cock.li doesn't parse your E-mail to provide you with targeted ads, nor do I read E-mail contents unless it's for a legal court order. However, it is 100% possible for me to read E-mail, and IMAP/SMTP doesn't provide user-side/client-side encryption, so you're just going to have to take my word for it. Any encryption implementation would still technically allow me to read E-mail, too. This was true for Lavabit as well -- while your E-mail was stored encrypted (only if you were a paid member, which most people forget), E-mail could still technically be intercepted while being received / sent (SMTP), or while being read by your mail client (IMAP). For privacy, I would recommend encrypting your E-mails using PGP using a mail client add-on like Enigmail.
This was originally followed by a quote from /g/, which has been redacted for obvious reasons (if you want it, you know where to find it), save this line:
>Now that I think about it, administering a mail host is exactly like being a nurse, only people die slightly less often.