Given sufficient mutuality, you can have some assurance of e2e but your risk here is your own and the other ends OPSEC which is all the NSA guidance really can

Given sufficient mutuality, you can have some assurance of e2e but your risk here is your own and the other ends OPSEC which is all the NSA guidance really can re-inforce: the more people and devices you bring into an exchange the less likely it is you really have secure communications.