My certificate was working fine to sign emails yesterday. I don't encrypt, just sign.

Now I am unable to sign.  My certificate reports as valid.  (Outlook 2013 - Windows 8.1 Enterprise)

Found a number of entries for mismatched email addresses and for encrypted emails.  None of those suggestions apply as my email address is contained within my certificate despite the statement in the error message that a certificate matching my email address could not be found. 

Full error text:

Invalid Certificate

Microsoft Outlook cannot sign or encrypt this message because there are no certificates which can be used to send from the e-mail address 'xxxxxx @ yyyyy.zzz. Either get a new digital ID to use with this account, or use the Accounts button to send the message from an account that you have certificates for.

• Edited by BRuce Young 6 hours 37 minutes ago

I recommend that you post this in the Outlook Forum:  http://social.technet.microsoft.com/Forums/en-US/outlook/threads

Hi,

Please check the following: Check Tools | Trust Center | E-mail Security and make sure that "Encrypt Contents and attachments" isn't checked.

Add digital signatures to outgoing messages

Click on Tools > Trust Center > Trusted Publisher > delete the digital signature(s) if it is available in the list

Also better to have a look at the article: https://support.microsoft.com/en-us/kb/884738  

If it doesn't work, as the issue is related to outlook side, this forum focuses on some general discussion about Exchange.

I suggest we can ask a question in Microsoft Outlook forum for more help :

https://social.technet.microsoft.com/Forums/office/en-US/home?forum=outlook

Regards,

David 

David,

I specifically stated that I was not encrypting, just signing.

I will ask the question in the Outlook Forum.

Bruce