certificate for noreply mailbot, client mail delivery, trustable signs

Hi everybody!
I need some support about email certificates. Sorry for my bad english, i try to make my best :slight_smile:

We are using the SMTP bot to deliver mail for our clients & we would like to use a certificate to:

  1. be sure out letters are not in spam folders (to make trustable sign)
  2. be sure all of the content (styles, liks, pictures, etc) are displayed correctly & are not disabled as for junk email
  3. if the certificate will provide some encryption it’s very good (because sometimes we send private information) BUT ONLY if our clients don’t need some specific programs to decrypt these letters, its very important (our clients can use yahoo, gmail, or even their own servers, as client-program they can use anything too: web-interfaces, outlook, the bat, etc).

It’s necessary all mail was sent is delivered carefully & is not marked as junk/spam & is displayed correctly.
Can we use some of your email certificates to solve there problems? How much it can cost?

We are currently using freebsd.