Package: exim4 Version: 4.92-8+deb10u4 Severity: normal Please could you compile the exim4 packages with AUTH_EXTERNAL=yes set in the Makefile? This is needed for sending mail with TLS certificate authentication using K-9 Mail which requires SASL EXTERNAL. The new "external" driver was committed in January 2019:
https://github.com/Exim/exim/commit/b53c265b5c
