Good question. I understand the intent is to ensure our downline receive all our communication that is important for our business.
More that to ensure our PSAs & CSAs receive, we need to ensure email ID provided are still active per my opinion.
You need to first do below steps:-
Go to Hot Spots -> Genealogy
Once you get the full list of active PSAs and CSAs, see bottom of the page where you can download PSAs list and CSAs list separately in excel format.
Once you get their email IDs, you can send short email to see if there are any delivery failures. If you don't get, which means all email IDs are valid and active.
Now, you are sure that they get all your email messages.
Most of the problem of us is whether they reach to it.. that depends on how serious they are considering SFI business.