If you're up for friendship, or CM penpals, age is irrelevant and the experience can bring a lot of enjoyment to those who participate. If you're interested in dating potential only and want to hold the younger group at bay, you can politely inform them that you regard the age difference as too significant. If they don't take the hint, you can be more blunt and tell them you're not interested.
Be glad you're getting some attention. You just don't know when someone might have an older, eligibile brother and that's the reason for the contact.
I have yet to meet a man of any age who wants to be penpals. Perhaps I am overly cynical, but experience leads me to assume when I am contacted by men 10 or more years younger, that he is
a. a scammer thinking older women are the easiest marks
b. one of the many men on dating sites who is looking for a partner to "talk dirty" to
c. someone who thinks that older women are desparate for sex and therefore easy to get in bed.
Most of their messages start out with " I've always liked mature women" and if you get to know them and they are not scammers looking for money, they are men who have learned to use older women for a variety of other needs including feeding their egos. I suppose its possible that a younger man just happens to find me attractive and is just a nice person, but I havnt met any yet.
I wont get into men my own age who are looking for 45 year olds, because that has been commented on many, many times before.