smbmsg_t subnum element has been removed (unused).

src/sbbs3/readmail.cpp

@@ -210,7 +210,6 @@ void sbbs_t::readmail(uint usernumber, int which)
 
 		if(domsg && !(sys_status&SS_ABORT)) {
 
-			msg.subnum=INVALID_SUB;
 			show_msg(&msg
 				,msg.from_ext && msg.idx.from==1 && !msg.from_net.type
 					? 0:P_NOATCODES);