The best way to confirm that they receive your mails include:
1) When the reply your mails, ask you questions
2) When they follow the instructions you gave them, evident in their growth
3) When you PSAs and CSAs give you an Awesome sponsor rating every month
4) Engage them in live chat when you meet them online
5) When they become leaders, then you know they have learnt something frow you that is now been passed on to others
