No particular reason input.msg should be uppercase here.

src/sbbs3/email.cpp

@@ -101,7 +101,7 @@ bool sbbs_t::email(int usernumber, char *top, char *subj, long mode)
 	if(cfg.sys_misc&SM_DELREADM)
 		msgattr|=MSG_KILLREAD;
 
-	sprintf(msgpath,"%sINPUT.MSG", cfg.node_dir);
+	sprintf(msgpath,"%sinput.msg", cfg.node_dir);
 	username(&cfg,usernumber,str2);
 	if(!writemsg(msgpath,top,title,mode,INVALID_SUB,str2)) {
 		bputs(text[Aborted]);

src/sbbs3/postmsg.cpp

@@ -189,7 +189,7 @@ bool sbbs_t::postmsg(uint subnum, smbmsg_t *remsg, long wm_mode)
 	if(cfg.sub[subnum]->misc&SUB_NAME)
 		bputs(text[UsingRealName]);
 
-	sprintf(str,"%sINPUT.MSG",cfg.node_dir);
+	sprintf(str,"%sinput.msg",cfg.node_dir);
 	if(!writemsg(str,top,title,wm_mode,subnum,touser)
 		|| (long)(length=flength(str))<1) {	/* Bugfix Aug-20-2003: Reject negative length */
 		bputs(text[Aborted]);