Understanding Penneo email signature validity warnings
Penneo email signature validity warnings are unrelated to any signatures contained within the documents sent for signature. These warning messages appear because the recipient’s email client, such as Microsoft Outlook, does not recognize the specific certificate Penneo uses to sign outgoing emails. Most often, the message is triggered when the email client cannot validate the certificate against its known certificate authorities.
Penneo email certificate provider
All emails sent out by Penneo are signed with a digital certificate to ensure authenticity. Penneo uses GlobalSign as the certificate provider for all outgoing emails. If an email client is not configured to recognize GlobalSign or cannot reach the provider to verify the status, it may display a validity warning to the user.
Microsoft support for email digital signatures
Users experiencing these warnings in Microsoft products can refer to the official documentation for assistance. This article at Microsoft support explains the issue in detail: Verify the digital signature on a signed email message