* *No key*: there is no PGP key available for one of the listed email addresses
* *Missing key for encryption*: there is probably a key selected in FairEmail that does not exist in the OpenKeychain app anymore. Resetting the key (see above) will probably fix this problem.
* *Key for signature verification is missing*: the public key for the sender is not available in the OpenKeychain app. This can also be caused by Autocrypt being disabled in the encryption settings or by the Autocrypt header not being sent.
* *OpenPgp error 0: null*: please check the key in the OpenKeychain app and make sure there are no conflicting identities for the key and make sure all email addresses are lowercase.
* *OpenPgp error 0: null*: please check the key in the OpenKeychain app and make sure there are no conflicting identities for the key and make sure all email addresses are lowercase. Also, make sure the key can be used to sign/encrypt and isn't for encrypting/signing only.