Here is another tip for managing phone calls: you can install a call blocker with "whitelist" capability (for example IB-120 from hqtelecom.com). It is so small and plain looking that it doesn't draw much attention and is easily hidden. It allows you to program up to 120 phone numbers that will be allowed through, and it will block all other calls. So, only friends, family, and "approved" businesses like the bank and doctor's office will ever get through. If the number is not programmed into the box, it simply gets disconnected. We find this necessary for my mother-in-law, who is unable to not answer the phone or to tell someone "no". Also, we are getting her a phone that does not display the caller ID because she will go through her list of calls that have come in and try to call them back. Happily, most scammers and call centers use a non-functional number for their caller ID, but it is still a danger that she will call someone and agree to give money or buy something. We have had to take away her checkbook and her credit cards, which wasn't easy. We had to make it seem like she couldn't find them, and eventually she lost track and stopped looking for them. That won't work on everyone, though, and there is always the danger that she'll all of a sudden realize that she wants those things and we'll have to deal with it in a different way. It also makes us feel really guilty, even though we know it is for her own good.
Also, we have a huge problem with door-to-door salespeople. We have put a "NO SOLICITING" sign on her front door, but the worst ones just ignore that. We tried living with her and never leaving her unsupervised, but she did not like that at all. She wants to feel independent. Now we live next door and visit her twice a day. After years of being frustrated by all the appointments for construction estimates and bogus contracts that she signed, my husband wrote his Mom a letter explaining that she doesn't need any work done on her house or yard and that she should talk to him about anything that anyone tries to sell her. She keeps the letter on her kitchen counter and it seems to be helping.
The most effective thing we do, however, is going to see her twice a day, every day. Even though she still gets into trouble sometimes, we usually catch it right away. And yes, we take her mail whenever possible, because it is almost all dangerous to her! I like the PO Box idea - we may have to use that one!
I hope these experiences and ideas are helpful for someone out there!