Yes, I have and use TOR (The Onion Router). It is not email related, so let's take this thread there anyway.
This is about OPSEC (Operations Security). It is not for the faint of heart...
TOR attempts to make your 'net traffic hard to back-trace to you. It uses a layer of three separate server connections to keep your online identity hidden.
It CAN BE COMPROMISED by TOR servers which are not part of the TOR network or which have been compromised by deliberate intent and instead record information about the traffic they handle.
If, over time, a pattern can be identified which points back at you, then you are no longer anonymous.
There may be other vulnerabilities, but this one can work if you do a lot of TOR usage. Particularly if you maintain a single point of origin (you fail to change your ISP or Access Point (AP) frequently.
TOR has it's uses, but I cannot trust it as my main access route to the 'net. It can be used, with a fair amount of safety, if you restrict such usage to single messages separated by long time spans. It is NOT a failsafe option, so be aware of this when you do use TOR.
And now we return you to your regularly scheduled thread about email account providers.
[EDIT] on option with TOR is to use the TAILS operating system which is TOR plus a Linux bootable operating system written to a DVD or USB memory stick and NEVER installed to a hard drive.
TAILS - The Amnesic Incognito Live System
https://tails.boum.org/index.en.htmlThe idea on TAILS is to NOT offer an identifiable machine signature on messages sent using TOR and an email client or when connecting to another website using the built-in browser (Firefox custom version).