--- a/src/lib-lda/mail-deliver.c	Tue Feb 21 12:36:52 2017 +0200
+++ b/src/lib-lda/mail-deliver.c	Tue Feb 21 12:38:10 2017 +0200
@@ -43,6 +43,13 @@
 
 struct mail_deliver_mailbox {
 	union mailbox_module_context module_ctx;
+	bool delivery_box;
+};
+
+struct mail_deliver_transaction {
+	union mailbox_transaction_module_context module_ctx;
+
+	struct mail_deliver_cache cache;
 };
 
 static const char *lda_log_wanted_headers[] = {
@@ -223,6 +230,11 @@
 	}
 
 	*box_r = box = mailbox_alloc(ns->list, name, flags);
+	/* flag that this mailbox is used for delivering the mail. */
+	struct mail_deliver_mailbox *mbox = MAIL_DELIVER_STORAGE_CONTEXT(box);
+	i_assert(mbox != NULL);
+	mbox->delivery_box = TRUE;
+
 	if (mailbox_open(box) == 0)
 		return 0;
 
@@ -514,13 +526,15 @@
 	struct mail_deliver_mailbox *mbox = MAIL_DELIVER_STORAGE_CONTEXT(box);
 	struct mail_deliver_user *muser =
 		MAIL_DELIVER_USER_CONTEXT(box->storage->user);
+	struct mail_deliver_transaction *dt =
+		MAIL_DELIVER_STORAGE_CONTEXT(ctx->transaction);
 
 	if (mbox->module_ctx.super.save_finish(ctx) < 0)
 		return -1;
 
 	/* initialize most of the fields from dest_mail */
-	mail_deliver_log_update_cache(muser->deliver_ctx->cache,
-				      muser->deliver_ctx->pool, ctx->dest_mail);
+	mail_deliver_log_update_cache(&dt->cache, muser->deliver_ctx->pool,
+				      ctx->dest_mail);
 	return 0;
 }
 
@@ -530,13 +544,15 @@
 	struct mail_deliver_mailbox *mbox = MAIL_DELIVER_STORAGE_CONTEXT(box);
 	struct mail_deliver_user *muser =
 		MAIL_DELIVER_USER_CONTEXT(box->storage->user);
+	struct mail_deliver_transaction *dt =
+		MAIL_DELIVER_STORAGE_CONTEXT(ctx->transaction);
 
 	if (mbox->module_ctx.super.copy(ctx, mail) < 0)
 		return -1;
 
 	/* initialize most of the fields from dest_mail */
-	mail_deliver_log_update_cache(muser->deliver_ctx->cache,
-				      muser->deliver_ctx->pool, ctx->dest_mail);
+	mail_deliver_log_update_cache(&dt->cache, muser->deliver_ctx->pool,
+				      ctx->dest_mail);
 	return 0;
 }
 
@@ -573,14 +589,51 @@
 	mailbox_free(&box);
 }
 
+static struct mailbox_transaction_context *
+mail_deliver_transaction_begin(struct mailbox *box,
+			       enum mailbox_transaction_flags flags)
+{
+	struct mail_deliver_mailbox *mbox = MAIL_DELIVER_STORAGE_CONTEXT(box);
+	struct mail_deliver_user *muser =
+		MAIL_DELIVER_USER_CONTEXT(box->storage->user);
+	struct mailbox_transaction_context *t;
+	struct mail_deliver_transaction *dt;
+
+	i_assert(muser != NULL);
+	i_assert(muser->deliver_ctx != NULL);
+
+	t = mbox->module_ctx.super.transaction_begin(box, flags);
+	dt = p_new(muser->deliver_ctx->pool, struct mail_deliver_transaction, 1);
+
+	MODULE_CONTEXT_SET(t, mail_deliver_storage_module, dt);
+	return t;
+}
+
 static int
 mail_deliver_transaction_commit(struct mailbox_transaction_context *ctx,
 				struct mail_transaction_commit_changes *changes_r)
 {
 	struct mailbox *box = ctx->box;
-	union mailbox_module_context *mbox = MAIL_DELIVER_STORAGE_CONTEXT(box);
+	struct mail_deliver_mailbox *mbox = MAIL_DELIVER_STORAGE_CONTEXT(box);
+	struct mail_deliver_transaction *dt = MAIL_DELIVER_STORAGE_CONTEXT(ctx);
+	struct mail_deliver_user *muser =
+		MAIL_DELIVER_USER_CONTEXT(box->storage->user);
+
+	i_assert(dt != NULL);
+	i_assert(muser != NULL);
+	i_assert(muser->deliver_ctx != NULL);
 
-	if (mbox->super.transaction_commit(ctx, changes_r) < 0)
+	/* sieve creates multiple transactions, saves the mails and
+	   then commits all of them at the end. we'll need to keep
+	   switching the deliver_ctx->cache for each commit.
+
+	   we also want to do this only for commits generated by sieve.
+	   other plugins or storage backends may be creating transactions as
+	   well, which we need to ignore. */
+	if (mbox->delivery_box)
+		muser->deliver_ctx->cache = &dt->cache;
+
+	if (mbox->module_ctx.super.transaction_commit(ctx, changes_r) < 0)
 		return -1;
 
 	if (array_count(&changes_r->saved_uids) > 0) {
@@ -617,6 +670,7 @@
 	box->vlast = &mbox->module_ctx.super;
 	v->save_finish = mail_deliver_save_finish;
 	v->copy = mail_deliver_copy;
+	v->transaction_begin = mail_deliver_transaction_begin;
 	v->transaction_commit = mail_deliver_transaction_commit;
 
 	MODULE_CONTEXT_SET(box, mail_deliver_storage_module, mbox);