GPGMail: encryption failed: Unusable public key

Jason Kay's Avatar

Jason Kay

21 Nov, 2017 03:07 AM

I get the following message when trying to encrypt a message. I have tried restarting the computer, and it’s still there:

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 with the following error description:

gpg: 21A0183AE1A9F2EB6D765FA4747F8017DAD8CAD2: skipped: Unusable public key
gpg: [stdin]: encryption failed: Unusable public key

The problem occurs not when sending the email, but when trying to encrypt it in the first place in Mac Mail. I can sign the email, but I can’t encrypt it without the error popping up.

macOS           10.12.6     16G1036
GPG Suite       2017.1      2002    (4161887)
GPGMail         2.7         1242    (4272b15)
GPG Keychain    1.4         1377    (3384573)
GPGServices     1.11.1      961     (d6060fa)
MacGPG2         2.2.0       893     (ab15b08)
GPGPreferences  2.1         977     (b1e419a)
Libmacgpg       0.8         819     (c8cf2e0)
pinentry        0.9.7       6       (6aeb033)
  1. Support Staff 1 Posted by Steve on 22 Nov, 2017 03:37 PM

    Steve's Avatar

    Hi Jason,

    welcome to the GPGTools support platform. Sorry you are having problems using GPG Suite.

    The error message that "encryption failed" due to an "unusable public key" can be caused by an expired subkey in your own key.

    To find out, if your subkey is expired:

    1. double click your sec / pub key in GPG Keychain
    2. navigate to the "Subkey" tab
    3. check the validity field

    In case your subkey is indeed expired, please click the cogwheel-icon to update the expiration date. Your key then should be working as expected. Restart and send yourself an encrypted and signed email to test functionality.

    Let me know if that worked,

    Best regards,

  2. 2 Posted by Jason Kay on 22 Nov, 2017 03:44 PM

    Jason Kay's Avatar

    Thank you very much. The key was expired and I fixed it. I instructed all who I communicate with to update my key from the server. Thank you!

  3. Support Staff 3 Posted by Steve on 22 Nov, 2017 03:49 PM

    Steve's Avatar

    Perfect. Glad, this is solved for you.

    We have an open ticket to improve the process of letting users known when their key will expire.

    I'm closing this discussion. Should you need further assistance or have questions you can re-open this discussion here or open a new one any time.


  4. Steve closed this discussion on 22 Nov, 2017 03:49 PM.

  5. Steve closed this discussion on 27 Aug, 2018 12:38 PM.

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