This depends largely on how the Private Email Network (PEN) you are using for a specific message is set up.
In many situations, it is necessary for the email2 message (or conversation / thread) to remain an email2 message, served by the same Private Email Network (PEN) for its entire life cycle so that tracking and audit integrity is not compromised. Additionally, many senders set specific security options for email2 message such as who can reply, forward, etc. Allowing users to reply to secure email2 messages as basic email messages would circumvent the original intentions of the sender.
If this is the case and your PEN is configured to enforce that every subsequent action to an email2 message is served by the same PEN, then recipients to your messages will have to reply using email2 on your PEN (tamper proof). They can, of course, take the content of your message, paste it into a new email1 message and send it along that way – or take a digital picture of their monitor and send the content via email1 - BUT at least the content did not leak from your PEN, making it very difficult for the recipient at fault to prove you did wrong doing (e.g. leak confidential information).
The purpose of email2 is NOT to protect the data after it made it safely to the intended recipients. Protecting content and attachments once they reside on the recipients' computer is something that many technologists have been trying to address for a long time. If this is the problem you are trying to address, we recommend that you look into Microsoft’s Information Rights Management (IRM) technology, which obviously works with email2.
// Last Edited: July 08