Issues forwarding S/MIME encrypted messages as attachments

Forwarding S/MIME encrypted emails (either sent emails or received emails) yields unexpected results. Recipients of these forwarded messages are not able to open them, which leads me to believe MailMate does not decrypt/re-encrypt messages to be readable.

Steps

1. Create an S/MIME encrypted message to yourself or someone else

2. Send the message

3. Find the sent message and forward it as an attachment

4. Encrypt the forwarded message to a new recipient with S/MIME

5. Send the forwarded message

   The recipient cannot read the attached message

6. Find the sent message from step 2 and forward it as an attachment

7. Do not encrypt the forwarded message

8. Send the forwarded message

   The recipient cannot read the attached message

Expected Results

MailMate decrypts and (optionally) re-encrypts attached messages as needed so that the recipient(s) I am forwarding them to can read them.

MailMate should guarantee the recipient can read my message forwarded as an attachment both when I choose to use encryption with the recipient and when I send it unencrypted. The end-user should be able to decide whether the previously encrypted content is OK to send unencrypted.

Actual Results

MailMate appears to treat the S/MIME encrypted messages as plain files and does not modify them; as a result, recipients cannot read the forwarded messages.