diff -r -u3 imap-4.5_orig/src/osdep/unix/env_unix.c imap-4.5/src/osdep/unix/env_unix.c
--- imap-4.5_orig/src/osdep/unix/env_unix.c	Wed Dec 16 01:51:20 1998
+++ imap-4.5/src/osdep/unix/env_unix.c	Thu Jun 17 00:00:06 1999
@@ -486,6 +486,7 @@
   struct passwd *pw;
   struct stat sbuf;
   char *s,tmp[MAILTMPLEN];
+  DRIVER *d;
   if (myUserName) fatal ("env_init called twice!");
 				/* myUserName must be set before dorc() call */
   myUserName = cpystr (user ? user : anonymous_user);
@@ -532,7 +533,12 @@
   if (!anonymous && !sharedHome && (pw = getpwnam ("imapshared")))
     sharedHome = cpystr (pw->pw_dir);
 				/* force default prototype to be set */
-  if (!createProto) createProto = &CREATEPROTO;
+  /* this hard-wires in a createProto of the INBOX format */
+  if (!createProto) {
+    createProto = ((d = mail_valid (NIL,"INBOX",NIL)) &&
+                     strcmp (d->name,"dummy")) ?
+                       ((*d->open) (NIL)) : &CREATEPROTO;
+  }
   if (!appendProto) appendProto = &EMPTYPROTO;
 				/* re-do open action to get flags */
   (*createProto->dtb->open) (NIL);
Only in imap-4.5/src/osdep/unix: env_unix.c.cproto