don't use NAMESPACE unless the server supports it

imap.c

@@ -410,6 +410,8 @@ imap_exec (imap_t * imap, const char *fmt, ...)
 			imap->have_starttls = 1;
 		    else if (!strcmp ("AUTH=CRAM-MD5", arg))
 			imap->have_cram = 1;
+		    else if (!strcmp ("NAMESPACE", arg))
+			imap->have_namespace = 1;
 		}
 #endif
 	    }
@@ -607,10 +609,9 @@ imap_open (config_t * box, unsigned int minuid)
 	ret = imap_exec (imap, "LOGIN \"%s\" \"%s\"", box->user, box->pass);
     }
 
-    if (!ret)
-    {
     /* get NAMESPACE info */
-	if (box->use_namespace && !imap_exec (imap, "NAMESPACE"))
+    if (!ret && box->use_namespace && imap->have_namespace &&
+	    !imap_exec (imap, "NAMESPACE"))
     {
 	/* XXX for now assume personal namespace */
 	if (is_list (imap->ns_personal) &&
@@ -620,7 +621,6 @@ imap_open (config_t * box, unsigned int minuid)
 	    ns_prefix = imap->ns_personal->child->child->val;
 	}
     }
-    }
 
     if (!ret)
     {

isync.h

@@ -130,6 +130,7 @@ typedef struct
     list_t *ns_personal;
     list_t *ns_other;
     list_t *ns_shared;
+    unsigned int have_namespace:1;
 #if HAVE_LIBSSL
     unsigned int have_cram:1;
     unsigned int have_starttls:1;