I get the message: unusable public key

vincent.rijmen's Avatar


29 Apr, 2016 09:42 AM


Mac OS X 10.11.4 (15E65)
Libmacgpg 0.6.1 752
GPGMail 2.6b2 1105b
GPG Keychain 1.2.1 1147
GPGServices 1.10.1 871
MacGPG2 2.0.28 855
GPGPreferences 1.5 846

Starting this morning, I get windows like the following. First I thought there was a problem with my recipient's key, but the problem occurs for all my recipients.

Encrypting your message failed because an unknown error has occured

Unfortunately GPGMail can't handle the error at this point.

Should your problem persist, please contact us at https://gpgtools.tenderapp.com/ with the following error description:

gpg: 0FA31D056A09368E806EA42CF64F33193AC12B09: skipped: Unusable public key
gpg: -&5: encryption failed: Unusable public key

What did you expect instead

Before, encryption to these email addresses worked.

Describe steps leading to the problem.

I start to draft a mail and then I get the window, even before I push the "send" button.

Are you using any other Mail.app plugins?


  1. 1 Posted by vincent.rijmen on 29 Apr, 2016 10:00 AM

    vincent.rijmen's Avatar

    Additional information: this morning, my own public key expired. I extended its lifetime, but I don't know how quickly this information spreads. Still, my client should never have to use my public key.

  2. 2 Posted by vincent.rijmen on 29 Apr, 2016 10:56 AM

    vincent.rijmen's Avatar

    Sorry. I now found out from your knowledge base why the client needs my own public key. It seems that after the information about the extension of my key's lifetime spread back to my own client, everything works again.
    Finally, the only thing I can comment is that your error messages could be more fool-proof (where the fool = me).

  3. Support Staff 3 Posted by Steve on 29 Apr, 2016 11:24 AM

    Steve's Avatar

    Hey Vincent,

    seems everything got solved already. I was suspecting an expired key at first. Good to know that was the culprit here.

    Mail.app needs to be restarted to pick up the key change, once you've extended the lifetime of your key.

    Your own public key is needed to encrypt any outgoing encrypted mail. Otherwise it would be impossible to read any sent mail at a later point in time.

    The error message is pretty confusing and far from perfect. We have a ticket for this problem. I connected this discussion with the existing ticket. That means, should this discussion get closed, it will be re-opened as soon as the ticket is closed. That way you'll stay in the loop and get notified as soon as we have news. Feel free to open a new discussions should you run into further problems or need assistance.

    Do you have further questions, or can I close this discussion?

    Kind regards,

  4. 4 Posted by vincent.rijmen on 29 Apr, 2016 11:41 AM

    vincent.rijmen's Avatar

    Dear Steve,

    Thanks for your quick reaction and sorry for your trouble.
    You can close this discussion.


  5. Support Staff 5 Posted by Steve on 29 Apr, 2016 11:42 AM

    Steve's Avatar

    No worries at all. That unhelpful error message is on our side. We hope to have a better solution for this in the future.

    Glad, this is solved for you. I'm closing this discussion. If you need further assistance or have questions you can re-open this discussion here or open a new one any time.

    Have a great day (:

  6. Steve closed this discussion on 29 Apr, 2016 11:42 AM.

  7. Steve closed this discussion on 27 Aug, 2018 12:31 PM.

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