Error message

Error message:

• This message has an invalid Digital Signature. Open the Message for more information

The warning got nothing to do with any signatures in the documents sent for signature. The message appears because the email client (Outlook or something similar) does not know the certificate Penneo uses to sign their emails. All emails sent out is signed with a certificate. Penneo's certificate provider for emails is GlobalSign. The reason for the message is most likely that your email client can't validate the certificate.

Article at Microsoft support that explains the issue: Verify the digital signature on a signed email message