Um? How many is 25%? If you emailed 100 people and 25 opened it, I'm guessing the problem is either

a) you're not emailing the right people

b) your take on 'helpful data' doesn't match your readers' take.

c) email is so last century they can't really believe you're using it

What does your call to action (email link) do? send a reply? sign them up? something else?

Frankly, when I see a "click and reply" I usually figure it's spam and toss it. A LOT of people want to know what my live email address is. I think that if I reply, they'll know for sure and they'll send me more. I don't even bother with "take me off your list" links in email figuring that it's just confirming my email address for people I don't want to hear from ... If I'm really tired of getting email from that address, I just blacklist it and move on.

(I may be a bit nastier than most but I get 300-500 spam mails a day. I have no time for people who email me asking me to do anything unless it's my boss, my editor, or my wife.)