+ 5. DSCP support for outbound connections: on a transport using the smtp driver,
+ set "dscp = ef", for instance, to cause the connections to have the relevant
+ DSCP (IPv4 TOS or IPv6 TCLASS) value in the header. Supported values depend
+ upon system libraries. "exim -bI:dscp" to list the ones Exim knows of.
+ You can also set a raw number 0..0x3F.
+