My 89 year old MIL got scammed by telephone. They had her absolutely convinced that that her oldest grandkid was in dire need, and also that she shouldn't tell ANYONE about it. We are very thankful she couldn't drive and never gave any money away. I found out because MIL couldn't stop crying and even then it took me about 30 minutes to pry the information out of her. And, it took EVEN longer to convince her that the grandchild was perfectly fine. (Not even talking to the grandchild had her convinced. )
We switched her to ATT Uverse. It has a setting that you access online where you can enter in 30 different phone numbers, and only those phone numbers are allowed to call in. Every other phone number is blocked. This works for her very well. She likes knowing that if her phone rings it is someone she knows. It is more expensive than her previous plan, but for her situation is totally worth it!
Also, all friends and family know also, so they know to call me or my husband if they are calling from a different number.
We don't have anything that works really well for mail. But, I am over there almost every day, and I bring in her mail for her, but conveniently go through it and throw away all junk mail before she ever sees it.