E-mail encryption with mailbox.org Guard is 100% compatible with the OpenPGP Standard.

The web interface of mailbox.org allows the sending, receiving, signing, and verification of PGP/MIME- and PGP/Inline-encrypted e-mails. Users of mailbox.org can thus communicate securely with everyone else who uses a PGP-compatible e-mail client or -plugin.

By default a freshly activated mailbox.org Guard creates a RSA 2048 bit key pair . As of December 2020 this is considered sufficiently secure for day-to-day use.
Those who have higher protection requirements, may want to use a ECC Curve25519 PGP pair. This has to be created manually.

Afterwards it has to be imported manually into the mailbox.org-Guard.