Export your OpenPGP key from OpenKeychain as an Autocrypt setup message. Send the setup message to your desktop email and download the attachment. In Thunderbird, go to Account Settings > End-to-End Encryption for your account and select OpenPGP Key Manager. Use File > Import Keys from File to import the downloaded Autocrypt file. This should prompt you to enter the passphrase and complete the import.

Thanks for the reply but i already tried that. It doesn't even recognize the autocrypt-setup-message file as a GnuPg file and says 'Error! failed to import file'. i tried to add the autocrypt Thunderbird-addon but it's not compatible with the current Thunderbird version.

Henry Thomas said

Export your OpenPGP key from OpenKeychain as an Autocrypt setup message. Send the setup message to your desktop email and download the attachment. In Thunderbird, go to Account Settings > End-to-End Encryption for your account and select OpenPGP Key Manager. Use File > Import Keys from File to import the downloaded Autocrypt file. This should prompt you to enter the passphrase and complete the import.

It sounds like Thunderbird isn’t automatically detecting the Autocrypt setup message file for import. You can try manually importing your OpenPGP key instead. Here’s how:

Extract the Key from OpenKeychain:

Open OpenKeychain on your Android device. Select your key, then go to Export > File, and save it as an .asc file. Transfer this file to your desktop. Manually Import the Key in Thunderbird:

Open Thunderbird and go to Tools > OpenPGP Key Manager. Click File > Import Public Key(s) from File. Select the .asc file and follow the prompts to enter your passphrase. If you’re still looking to use the Autocrypt setup message method, you might try renaming the file to ensure it has a .autocrypt extension before opening it in Thunderbird.