If it is up to you to organize all of these folks it sounds like you are the boss. Can you possibly ask them if they have email, how often they check it and depending on the situation...can you demand that they check their email once a day or twice a week or something? The guy with the filter problem should be able to fix it to allow you in. Otherwise perhaps one person can be assigned to call him.

Having to call these folks is not time effective.

Good luck. :-)