... almost 80% of the over 50 age group does not respond to email marketing, preferring to use email to communicate with friends.... However ... 36% of this age group are happy to communicate with brands online once initial contact has been made using other media.
Most donors (by a large margin) are over 50.
This is why it's critically important to segment your lists, whether they be email or direct mail, not everyone responds to the same stimulus.
For DECs, who have memberships largely over age 50, it's important to realize that pushing fundraising via your email lists isn't always the exact way to go. People have to be slowly but surely persuaded. My suggestion is to use your email list to send informational emails (like newsletters and event signups) to get your constituencies to recognize the value of opening that message from the local DEC. Over time, you'll develop the loyalty that's required to finally send a fundraising email.