1874354 - filters to forward emails should not forward encrypted emails unencrypted

Status: RESOLVED DUPLICATE of bug 1790736

(Thunderbird :: Filters, defect)

Description

[bugzilla]

Steps to reproduce:

Created a filter that forwards incoming mails to another email address.
Received encrypted emails (S/MIME or PGP).

Actual results:

The incoming encrypted emails will be forwarded unencrypted. This happens regardless of whether the email addresses to which messages are forwarded have S/MIME certificates or PGP keys themselves.

Expected results:

This is a security problem. The senders of encrypted emails have no way of knowing about the recipient's forwarding. All unencrypted forwarded messages are to be considered compromised.
I would expect that emails that are received in encrypted form should only be forwarded in encrypted form. If the email address to which it is forwarded does not have an S/MIME certificate or a PGP key, it should not be forwarded at all. Otherwise, the forwarded emails should be re-encrypted for these recipients.
This should be checked when the forwarding filter is created and a warning issued if necessary.
A warning or notice should also be issued if an encrypted email cannot be forwarded due to this policy.