mailbox Guard - external user unable to decrypt with password
I am evaluating mailbox.org service in comparison to others like Protonmail, Tutanota and Posteo.
I have been trying to use the Guard encryption function to send an encrypted email message to an external user - one of the other mail services as well as a Yahoo account and have been unable to decrypt the message using the Guard password.
The external user gets the message with link to the temporary mailbox and the instruction to Please provide your encryption password and I understood that they would just need to enter the Guard password that I created and shared with them. I opened the encrypted email as the mailbox user and tried the PGP inline, etc. but none of the external users can decrypt.
They get the Bad username/Password error message and are prompted to enter their username and password. If this is how it functions for external users this will be to complex a process for them. I used both Protonmail and Tutanota's encrypt function and it worked seamlessly for the external accounts, including for mailbox user.
I've looked at the knowledgebase, help sections but still can't do this basic function.