I have an end user who is trying to exchange encrypted messages with a person outside of our company domain.

When receiving emails from the user they receive a message that says:

Signed By: (There were errors displaying the signers of this message, click on the signature icon for more details.)

However, when you click on the signature icon it says:

The digital signature on this message is Valid and Trusted.

Then when you look at the "Message Security Properties" it shows two layers, each with a green checkmark beside them. The layers are presented as below:

• Subject:
  • Digital Signature Layer

It also has:

 Description: OK: Signed message

The end result with all of this is that when the user on my side tries to send this user an encrypted message it says:

Microsoft Outlook had problems encrypting this message because the following recipients had missing or invalid certificates, or conflicting or unsupported encryption capabilities:



Continue will encrypt and send the message but the listed recipients may not be able to read it.

However, the only options you are actually given is "Send Unencrypted" and "CanceL" (Continue is grayed out).

If anybody can assist I would greatly appreciate it!