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Advocate I
Advocate I

Outlook action Forward_an_email_(V2) fails when email message is signed with unknown digital signature



We use flow to organize and process e-invoices from known suppliers and it works great, except for one. We've found out that this supplier sends us emails with digital signature that initially was recognized by outlook as impossible to verify it's validity. In case of emails from this supplier we get following error: Action 'Forward_an_email_(V2)' failed with message "The specified object was not found in the store., Cannot open attachment.".

Of course the message is in the mailbox and it contains the attachment. The only reason for that error we see is that message signature is invalid.

After opening message in outlook app the signature gets somehow validated and message doesn't have disclaimer about invalid signature, but how to solve this problem with the outlook connector activity?


Is there a workaround or solution for this situation?

Community Support
Community Support

Hi @tszalaj ,


Could you please share a screenshot of the email with it's message signature?

Could you please share a screenshot of the configuration of your flow and a screenshot of the run history when it is failed?


Best regards,



Community Support Team _ Alice Zhang
If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.



Thanks for replay. A brief flow explanation:

1. It starts with on new e-mail trigger, then exports mail for it's properties extraction and I check in sharepoint list if message sender is known (expected). That part works fine in defective scenario:

on new emailon new email

2. Problematic email is signed with signature that has invalid signature:

in problematic scenario email has unknown signaturein problematic scenario email has unknown signature

3. In outlook app I can see that signature is invalid because system cannot validate certificate used to sign the message:

in outlook desktop app that signature is invalid until CA certificate is openedin outlook desktop app that signature is invalid until CA certificate is opened

4. When I click "show details" the signature details panel on the left shows invalid signature, but when I hit "show certificate" on the bottom of left panel I get the certificate details (on the right panel) and the signature becomes valid. From that moment all emails from that sender in my outlook app have valid signature:


when CA certificate is opened the signature gets validated and email signature starts to be validwhen CA certificate is opened the signature gets validated and email signature starts to be valid


5. But that doesn't work for Flow. It still fails on email forward action saying that attachment was not found. That doesn't happen for emails that are not signed:



Error details: The specified object was not found in the store. Cannot open attachment.



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