gnutls
exim -DSERVER=server -bd -oX PORT_D
****
-client-gnutls 127.0.0.1 PORT_D
+# Have the client prefer RSA (but support ECDSA as well). That should get us RSA on both older and newer GnuTLS.
+client-gnutls -p NONE:+SIGN-RSA-SHA256:+SIGN-ECDSA-SHA512:+VERS-TLS-ALL:+ECDHE-RSA:+DHE-RSA:+RSA:+CIPHER-ALL:+MAC-ALL:+COMP-NULL:+CURVE-ALL:+CTYPE-X509 127.0.0.1 PORT_D
??? 220
ehlo rhu.barb
??? 250-
quit
??? 221
****
-client-gnutls 127.0.0.1 PORT_D
+client-gnutls -p NONE:+SIGN-RSA-SHA256:+SIGN-ECDSA-SHA512:+VERS-TLS-ALL:+ECDHE-RSA:+DHE-RSA:+RSA:+CIPHER-ALL:+MAC-ALL:+COMP-NULL:+CURVE-ALL:+CTYPE-X509 127.0.0.1 PORT_D
??? 220
ehlo rhu.barb
??? 250-
quit
??? 221
****
-client-gnutls HOSTIPV4 PORT_D
+client-gnutls -p NONE:+SIGN-RSA-SHA256:+SIGN-ECDSA-SHA512:+VERS-TLS-ALL:+ECDHE-RSA:+DHE-RSA:+RSA:+CIPHER-ALL:+MAC-ALL:+COMP-NULL:+CURVE-ALL:+CTYPE-X509 HOSTIPV4 PORT_D
??? 220
ehlo rhu.barb
??? 250-
starttls
??? 220
****
-client-gnutls HOSTIPV4 PORT_D DIR/aux-fixed/exim-ca/example.com/server2.example.com/server2.example.com.pem DIR/aux-fixed/exim-ca/example.com/server2.example.com/server2.example.com.unlocked.key
+client-gnutls -p NONE:+SIGN-RSA-SHA256:+SIGN-ECDSA-SHA512:+VERS-TLS-ALL:+ECDHE-RSA:+DHE-RSA:+RSA:+CIPHER-ALL:+MAC-ALL:+COMP-NULL:+CURVE-ALL:+CTYPE-X509 HOSTIPV4 PORT_D DIR/aux-fixed/exim-ca/example.com/server2.example.com/server2.example.com.pem DIR/aux-fixed/exim-ca/example.com/server2.example.com/server2.example.com.unlocked.key
??? 220
ehlo rhu.barb
??? 250-
quit
??? 221
****
+#
+#
+# A client that only talks RSA.
+#
+# We have to specify the key-exchange as well as the authentication, otherwise,
+# the GnuTLS server side being foolish - it picks an ECDSA cipher-suite and then can't use it :(
+# Possibly fixed in 3.6.x ?
+client-gnutls -p NONE:+SIGN-RSA-SHA256:+VERS-TLS-ALL:+ECDHE-RSA:+DHE-RSA:+RSA:+CIPHER-ALL:+MAC-ALL:+COMP-NULL:+CURVE-ALL:+CTYPE-X509 127.0.0.1 PORT_D
+??? 220
+ehlo rhu.barb
+??? 250-
+??? 250-
+??? 250-
+??? 250-
+??? 250-
+??? 250
+starttls
+??? 220
+mail from:<CALLER@test.ex>
+??? 250
+rcpt to:<CALLER@test.ex>
+??? 250
+DATA
+??? 3
+This is a test encrypted message.
+It should be sent under the RSA server cert and with an RSA cipher.
+.
+??? 250
+quit
+??? 221
+****
+#
+#
+# Make ECDSA authentication preferred (Older GnuTLS prefers RSA, it seems, Newer, ECDSA).
+client-gnutls -p NONE:+SIGN-ECDSA-SHA512:+VERS-TLS-ALL:+KX-ALL:+CIPHER-ALL:+MAC-ALL:+COMP-NULL:+CURVE-ALL:+CTYPE-X509 127.0.0.1 PORT_D
+??? 220
+ehlo rhu.barb
+??? 250-
+??? 250-
+??? 250-
+??? 250-
+??? 250-
+??? 250
+starttls
+??? 220
+mail from:<CALLER@test.ex>
+??? 250
+rcpt to:<CALLER@test.ex>
+??? 250
+DATA
+??? 3
+This is a test encrypted message.
+It should be sent under the EC server cert and with an ECDSA cipher.
+.
+??? 250
+quit
+??? 221
+****
killdaemon
exim -qf
****