I have a message with: Content-Transfer-Encoding: 8bit Content-Type: text/html; charset=koi8-r
Does your product support this encoding?
Yes, Mail.dll supports this charset correctly, both processing email messages and creating and sending emails.
In both cases you'll use regular .NET strings.
You can download Mail.dll email component here: https://www.limilabs.com/mail/download
If you run in to problems just let us know.