- Go to Settings -> Messages -> Encryption and click on your Personal key for which you would like to change the expiration date of.
- Click on Edit next to the current Expiration date.
- Enter your passphrase for that OpenPGP keypair and click on OK.
- Select the new Expiration date OR Check This key does not expire box.
- If you already have published your OpenPGP public key on Public key servers, then Check Publish on public key server box to update your OpenPGP public key expiration date on public key servers.
- Click on Save.
Note: While you can still decrypt emails using an expired and/or revoked OpenPGP key pair, you cannot sign emails using your expired and/or revoked OpenPGP key pair. Also sending an encrypted email using expired and/or revoked public key of the recipient is not allowed.