Services like Lacre [1] on Disroot and Inbound Encryption on Posteo [2]
offer to encrypt all incoming messages with the provided OpenPGP
public key. Resulting messages are encrypted, but not end-to-end encrypted
and not signed by the sender, therefore should not have a padlock displayed.
However, such encrypted and unsigned message is also not an indication
of an error on ongoing attack, so we shoud not report this as a problem
to the user.
[1] https://lacre.io/
[2] https://posteo.de/en/help/how-do-i-activate-inbound-encryption-with-my-public-pgp-key