If you head over to cryptomixer.io and start a mix then download the letter of guarantee you'll see the address is 1CrypMixUKiXduy6J42nEzm4Z9CpJuXptS which cryptomixer has specified is a scam address?
Prove it. Create a new session, download the letter and post the URL of the file here.
For example, here is one I just generated:
https://cryptomixer.io/api/v2/operations/ec5faf51-fdff-4aef-a54e-3788148419ad/letterOfGuarantee? (right address)
This proves the letter is actually coming from their website.