-# Too-small DH param (library limitation), from file
-exim -DSERVER=server -DDATA=DIR/aux-fixed/dh512 -bd -oX PORT_D
+# prime256v1
+# Oddly, 3.0.5 packets show an EC-groups negotiation of C:x255519 S:secp256r1 C:secp256r1 S:secp256r1.
+# Hoever, note that RFC 8446 (TLS1.3) does NOT include prime256v1 as one of the allowable
+# supported groups (and it's not in the client "supported groups" extension, so what we see seems good.
+exim -DSERVER=server -DDATA=prime256v1 -bd -oX PORT_D