--- a/src/lib-storage/mail-storage.c	Tue Sep 04 18:51:43 2012 +0300
+++ b/src/lib-storage/mail-storage.c	Tue Sep 04 19:04:52 2012 +0300
@@ -12,6 +12,7 @@
 #include "var-expand.h"
 #include "mail-index-private.h"
 #include "mail-index-alloc-cache.h"
+#include "mailbox-tree.h"
 #include "mailbox-list-private.h"
 #include "mail-storage-private.h"
 #include "mail-storage-settings.h"
@@ -1251,6 +1252,16 @@
 	return box->v.set_subscribed(box, set);
 }
 
+bool mailbox_is_subscribed(struct mailbox *box)
+{
+	struct mailbox_node *node;
+
+	i_assert(box->list->subscriptions != NULL);
+
+	node = mailbox_tree_lookup(box->list->subscriptions, box->vname);
+	return node != NULL && (node->flags & MAILBOX_SUBSCRIBED) != 0;
+}
+
 struct mail_storage *mailbox_get_storage(const struct mailbox *box)
 {
 	return box->storage;

--- a/src/lib-storage/mail-storage.h	Tue Sep 04 18:51:43 2012 +0300
+++ b/src/lib-storage/mail-storage.h	Tue Sep 04 19:04:52 2012 +0300
@@ -447,6 +447,10 @@
 /* Subscribe/unsubscribe mailbox. Subscribing to
    nonexistent mailboxes is optional. */
 int mailbox_set_subscribed(struct mailbox *box, bool set);
+/* Returns TRUE if mailbox is subscribed, FALSE if not. This function
+   doesn't refresh the subscriptions list, but assumes that it's been done by
+   e.g. mailbox_list_iter*(). */
+bool mailbox_is_subscribed(struct mailbox *box);
 
 /* Enable the given feature for the mailbox. */
 int mailbox_enable(struct mailbox *box, enum mailbox_feature features);