email-forwarding

I am trying to write a newsletter but I am having trouble hiding the responsive contents when I test on GMail . On Outlook and Yahoo everything is ok, but if I try to forward the e-mail the hidden contents are visible. I tested using : putsmail > I use this to send test on Outlook , Yahoo and GMail 1 . Yahoo > looks ok, but when I try to forward the e-mail the hidden content it's visible; 2. Outlook > looks ok, but when I try to forward the e-mail the hidden content it's visible; 3. GMail > the hidden content it's visible. mailchimp > this works for me to make tests only on Outlook and it

I'm trying to do what craigslist's anonymous email does, but with Rails, also on the cheap. It is important for me to be able to add a header to the email, which is why basic email forwarding doesn't work. One way I thought of was a SMTP server, whenever I read email via POP/IMAP, I then send an email to the true recipient of the email, with a proper FROM address and add in the header. This works, but a SMTP server is relatively costly. The other way is to forward/redirect the email, but add in the header in between. I can't find any services or gems to do this though. Please don't just say