diff --git a/src/Simplex/Messaging/Agent.hs b/src/Simplex/Messaging/Agent.hs
index d43473f65..1dd0b4c77 100644
--- a/src/Simplex/Messaging/Agent.hs
+++ b/src/Simplex/Messaging/Agent.hs
@@ -46,6 +46,7 @@ module Simplex.Messaging.Agent
     acceptConnection,
     subscribeConnection,
     sendMessage,
+    ackMessage,
     suspendConnection,
     deleteConnection,
   )
@@ -146,6 +147,9 @@ subscribeConnection c = withAgentEnv c . subscribeConnection' c
 sendMessage :: AgentErrorMonad m => AgentClient -> ConnId -> MsgBody -> m AgentMsgId
 sendMessage c = withAgentEnv c .: sendMessage' c
 
+ackMessage :: AgentErrorMonad m => AgentClient -> ConnId -> AgentMsgId -> m ()
+ackMessage c = withAgentEnv c .: ackMessage' c
+
 -- | Suspend SMP agent connection (OFF command)
 suspendConnection :: AgentErrorMonad m => AgentClient -> ConnId -> m ()
 suspendConnection c = withAgentEnv c . suspendConnection' c
@@ -236,6 +240,7 @@ processCommand c (connId, cmd) = case cmd of
   ACPT confId ownConnInfo -> acceptConnection' c connId confId ownConnInfo $> (connId, OK)
   SUB -> subscribeConnection' c connId $> (connId, OK)
   SEND msgBody -> (connId,) . MID <$> sendMessage' c connId msgBody
+  ACK msgId -> ackMessage' c connId msgId $> (connId, OK)
   OFF -> suspendConnection' c connId $> (connId, OK)
   DEL -> deleteConnection' c connId $> (connId, OK)
 
@@ -426,6 +431,20 @@ runSrvMsgDelivery c@AgentClient {subQ} srv = do
     notify :: ConnId -> ACommand 'Agent -> m ()
     notify connId cmd = atomically $ writeTBQueue subQ ("", connId, cmd)
 
+ackMessage' :: forall m. AgentMonad m => AgentClient -> ConnId -> AgentMsgId -> m ()
+ackMessage' c connId msgId = do
+  withStore (`getConn` connId) >>= \case
+    SomeConn _ (DuplexConnection _ rq _) -> ack rq
+    SomeConn _ (RcvConnection _ rq) -> ack rq
+    _ -> throwError $ CONN SIMPLEX
+  where
+    ack :: RcvQueue -> m ()
+    ack rq = do
+      let mId = InternalId msgId
+      withStore $ \st -> checkRcvMsg st connId mId
+      sendAck c rq
+      withStore $ \st -> updateRcvMsgAck st connId mId
+
 -- | Suspend SMP agent connection (OFF command) in Reader monad
 suspendConnection' :: AgentMonad m => AgentClient -> ConnId -> m ()
 suspendConnection' c connId =
@@ -491,14 +510,12 @@ processSMPTransmission c@AgentClient {subQ} (srv, rId, cmd) = do
           let msgHash = C.sha256Hash msg
           case parseSMPMessage msg of
             Left e -> notify $ ERR e
-            Right (SMPConfirmation senderKey cInfo) -> smpConfirmation senderKey cInfo
+            Right (SMPConfirmation senderKey cInfo) -> smpConfirmation senderKey cInfo >> sendAck c rq
             Right SMPMessage {agentMessage, senderMsgId, senderTimestamp, previousMsgHash} ->
               case agentMessage of
-                HELLO verifyKey _ -> helloMsg verifyKey msgBody
-                REPLY qInfo -> replyMsg qInfo
+                HELLO verifyKey _ -> helloMsg verifyKey msgBody >> sendAck c rq
+                REPLY qInfo -> replyMsg qInfo >> sendAck c rq
                 A_MSG body -> agentClientMsg previousMsgHash (senderMsgId, senderTimestamp) (srvMsgId, srvTs) body msgHash
-          sendAck c rq
-          return ()
         SMP.END -> do
           removeSubscription c connId
           logServer "<--" c srv rId "END"
diff --git a/src/Simplex/Messaging/Agent/Protocol.hs b/src/Simplex/Messaging/Agent/Protocol.hs
index 684a7e828..c704960a2 100644
--- a/src/Simplex/Messaging/Agent/Protocol.hs
+++ b/src/Simplex/Messaging/Agent/Protocol.hs
@@ -172,7 +172,7 @@ data ACommand (p :: AParty) where
   SENT :: AgentMsgId -> ACommand Agent
   MERR :: AgentMsgId -> AgentErrorType -> ACommand Agent
   MSG :: MsgMeta -> MsgBody -> ACommand Agent
-  -- ACK :: AgentMsgId -> ACommand Client
+  ACK :: AgentMsgId -> ACommand Client
   -- RCVD :: AgentMsgId -> ACommand Agent
   OFF :: ACommand Client
   DEL :: ACommand Client
@@ -469,6 +469,7 @@ commandP =
     <|> "SENT " *> sentResp
     <|> "MERR " *> msgErrResp
     <|> "MSG " *> message
+    <|> "ACK " *> ackCmd
     <|> "OFF" $> ACmd SClient OFF
     <|> "DEL" $> ACmd SClient DEL
     <|> "ERR " *> agentError
@@ -485,6 +486,7 @@ commandP =
     sentResp = ACmd SAgent . SENT <$> A.decimal
     msgErrResp = ACmd SAgent <$> (MERR <$> A.decimal <* A.space <*> agentErrorTypeP)
     message = ACmd SAgent <$> (MSG <$> msgMetaP <* A.space <*> A.takeByteString)
+    ackCmd = ACmd SClient . ACK <$> A.decimal
     msgMetaP = do
       integrity <- msgIntegrityP
       recipient <- " R=" *> partyMeta A.decimal
@@ -526,6 +528,7 @@ serializeCommand = \case
   MERR mId e -> "MERR " <> bshow mId <> " " <> serializeAgentError e
   MSG msgMeta msgBody ->
     "MSG " <> serializeMsgMeta msgMeta <> " " <> serializeBinary msgBody
+  ACK mId -> "ACK " <> bshow mId
   OFF -> "OFF"
   DEL -> "DEL"
   CON -> "CON"
diff --git a/src/Simplex/Messaging/Agent/Store.hs b/src/Simplex/Messaging/Agent/Store.hs
index bf5e6921f..fd8b3ced6 100644
--- a/src/Simplex/Messaging/Agent/Store.hs
+++ b/src/Simplex/Messaging/Agent/Store.hs
@@ -60,6 +60,8 @@ class Monad m => MonadAgentStore s m where
   getPendingMsgData :: s -> ConnId -> InternalId -> m (SndQueue, MsgBody)
   getPendingMsgs :: s -> ConnId -> m [PendingMsg]
   getMsg :: s -> ConnId -> InternalId -> m Msg
+  checkRcvMsg :: s -> ConnId -> InternalId -> m ()
+  updateRcvMsgAck :: s -> ConnId -> InternalId -> m ()
 
 -- * Queue types
 
diff --git a/src/Simplex/Messaging/Agent/Store/SQLite.hs b/src/Simplex/Messaging/Agent/Store/SQLite.hs
index f74c705b1..5d63af27c 100644
--- a/src/Simplex/Messaging/Agent/Store/SQLite.hs
+++ b/src/Simplex/Messaging/Agent/Store/SQLite.hs
@@ -437,7 +437,35 @@ instance (MonadUnliftIO m, MonadError StoreError m) => MonadAgentStore SQLiteSto
         <$> DB.query db "SELECT internal_id FROM snd_messages WHERE conn_alias = ? AND snd_status = ?" (connId, SndMsgCreated)
 
   getMsg :: SQLiteStore -> ConnId -> InternalId -> m Msg
-  getMsg _st _connAlias _id = throwError SENotImplemented
+  getMsg _st _connId _id = throwError SENotImplemented
+
+  checkRcvMsg :: SQLiteStore -> ConnId -> InternalId -> m ()
+  checkRcvMsg st connId msgId =
+    liftIOEither . withTransaction st $ \db ->
+      hasMsg
+        <$> DB.query
+          db
+          [sql|
+            SELECT conn_alias, internal_id
+            FROM rcv_messages
+            WHERE conn_alias = ? AND internal_id = ?
+          |]
+          (connId, msgId)
+    where
+      hasMsg :: [(ConnId, InternalId)] -> Either StoreError ()
+      hasMsg r = if null r then Left SEMsgNotFound else Right ()
+
+  updateRcvMsgAck :: SQLiteStore -> ConnId -> InternalId -> m ()
+  updateRcvMsgAck st connId msgId =
+    liftIO . withTransaction st $ \db -> do
+      DB.execute
+        db
+        [sql|
+          UPDATE rcv_messages
+          SET rcv_status = ?, ack_brocker_ts = datetime('now')
+          WHERE conn_alias = ? AND internal_id = ?
+        |]
+        (AcknowledgedToBroker, connId, msgId)
 
 -- * Auxiliary helpers
 
diff --git a/tests/AgentTests.hs b/tests/AgentTests.hs
index 080db2b55..545bcece4 100644
--- a/tests/AgentTests.hs
+++ b/tests/AgentTests.hs
@@ -111,13 +111,17 @@ testDuplexConnection _ alice bob = do
   alice #: ("4", "bob", "SEND :how are you?") #> ("4", "bob", MID 2)
   alice <# ("", "bob", SENT 2)
   bob <#= \case ("", "alice", Msg "hello") -> True; _ -> False
+  bob #: ("12", "alice", "ACK 1") #> ("12", "alice", OK)
   bob <#= \case ("", "alice", Msg "how are you?") -> True; _ -> False
+  bob #: ("13", "alice", "ACK 2") #> ("13", "alice", OK)
   bob #: ("14", "alice", "SEND 9\nhello too") #> ("14", "alice", MID 3)
   bob <# ("", "alice", SENT 3)
   alice <#= \case ("", "bob", Msg "hello too") -> True; _ -> False
+  alice #: ("3a", "bob", "ACK 3") #> ("3a", "bob", OK)
   bob #: ("15", "alice", "SEND 9\nmessage 1") #> ("15", "alice", MID 4)
   bob <# ("", "alice", SENT 4)
   alice <#= \case ("", "bob", Msg "message 1") -> True; _ -> False
+  alice #: ("4a", "bob", "ACK 4") #> ("4a", "bob", OK)
   alice #: ("5", "bob", "OFF") #> ("5", "bob", OK)
   bob #: ("17", "alice", "SEND 9\nmessage 3") #> ("17", "alice", MID 5)
   bob <# ("", "alice", MERR 5 (SMP AUTH))
@@ -140,13 +144,17 @@ testDuplexConnRandomIds _ alice bob = do
   alice #: ("3", bobConn, "SEND :how are you?") #> ("3", bobConn, MID 2)
   alice <# ("", bobConn, SENT 2)
   bob <#= \case ("", c, Msg "hello") -> c == aliceConn; _ -> False
+  bob #: ("12", aliceConn, "ACK 1") #> ("12", aliceConn, OK)
   bob <#= \case ("", c, Msg "how are you?") -> c == aliceConn; _ -> False
+  bob #: ("13", aliceConn, "ACK 2") #> ("13", aliceConn, OK)
   bob #: ("14", aliceConn, "SEND 9\nhello too") #> ("14", aliceConn, MID 3)
   bob <# ("", aliceConn, SENT 3)
   alice <#= \case ("", c, Msg "hello too") -> c == bobConn; _ -> False
+  alice #: ("3a", bobConn, "ACK 3") #> ("3a", bobConn, OK)
   bob #: ("15", aliceConn, "SEND 9\nmessage 1") #> ("15", aliceConn, MID 4)
   bob <# ("", aliceConn, SENT 4)
   alice <#= \case ("", c, Msg "message 1") -> c == bobConn; _ -> False
+  alice #: ("4a", bobConn, "ACK 4") #> ("4a", bobConn, OK)
   alice #: ("5", bobConn, "OFF") #> ("5", bobConn, OK)
   bob #: ("17", aliceConn, "SEND 9\nmessage 3") #> ("17", aliceConn, MID 5)
   bob <# ("", aliceConn, MERR 5 (SMP AUTH))
@@ -161,12 +169,15 @@ testSubscription _ alice1 alice2 bob = do
   bob #: ("13", "alice", "SEND 11\nhello again") #> ("13", "alice", MID 2)
   bob <# ("", "alice", SENT 2)
   alice1 <#= \case ("", "bob", Msg "hello") -> True; _ -> False
+  alice1 #: ("1", "bob", "ACK 1") #> ("1", "bob", OK)
   alice1 <#= \case ("", "bob", Msg "hello again") -> True; _ -> False
+  alice1 #: ("2", "bob", "ACK 2") #> ("2", "bob", OK)
   alice2 #: ("21", "bob", "SUB") #> ("21", "bob", OK)
   alice1 <# ("", "bob", END)
   bob #: ("14", "alice", "SEND 2\nhi") #> ("14", "alice", MID 3)
   bob <# ("", "alice", SENT 3)
   alice2 <#= \case ("", "bob", Msg "hi") -> True; _ -> False
+  alice2 #: ("22", "bob", "ACK 3") #> ("22", "bob", OK)
   alice1 #:# "nothing else should be delivered to alice1"
 
 testSubscrNotification :: Transport c => TProxy c -> (ThreadId, ThreadId) -> c -> IO ()
@@ -185,6 +196,7 @@ testMsgDeliveryServerRestart t alice bob = do
     bob #: ("1", "alice", "SEND 2\nhi") #> ("1", "alice", MID 1)
     bob <# ("", "alice", SENT 1)
     alice <#= \case ("", "bob", Msg "hi") -> True; _ -> False
+    alice #: ("11", "bob", "ACK 1") #> ("11", "bob", OK)
     alice #:# "nothing else delivered before the server is killed"
 
   alice <# ("", "bob", DOWN)
@@ -196,6 +208,7 @@ testMsgDeliveryServerRestart t alice bob = do
     bob <# ("", "alice", SENT 2)
     alice <# ("", "bob", UP)
     alice <#= \case ("", "bob", Msg "hello again") -> True; _ -> False
+    alice #: ("12", "bob", "ACK 2") #> ("12", "bob", OK)
 
   removeFile testStoreLogFile
   where
@@ -209,6 +222,7 @@ testMsgDeliveryAgentRestart t bob = do
       alice #: ("1", "bob", "SEND 5\nhello") #> ("1", "bob", MID 1)
       alice <# ("", "bob", SENT 1)
       bob <#= \case ("", "alice", Msg "hello") -> True; _ -> False
+      bob #: ("11", "alice", "ACK 1") #> ("11", "alice", OK)
       bob #:# "nothing else delivered before the server is down"
 
     bob <# ("", "alice", DOWN)
@@ -226,6 +240,7 @@ testMsgDeliveryAgentRestart t bob = do
         _ -> False
       bob <# ("", "alice", UP)
       bob <#= \case ("", "alice", Msg "hello again") -> True; _ -> False
+      bob #: ("12", "alice", "ACK 2") #> ("12", "alice", OK)
 
   removeFile testStoreLogFile
   removeFile testDB
diff --git a/tests/AgentTests/FunctionalAPITests.hs b/tests/AgentTests/FunctionalAPITests.hs
index c9903fe85..008e0c14b 100644
--- a/tests/AgentTests/FunctionalAPITests.hs
+++ b/tests/AgentTests/FunctionalAPITests.hs
@@ -65,13 +65,17 @@ testAgentClient = do
     2 <- sendMessage alice bobId "how are you?"
     get alice ##> ("", bobId, SENT 2)
     get bob =##> \case ("", c, Msg "hello") -> c == aliceId; _ -> False
+    ackMessage bob aliceId 1
     get bob =##> \case ("", c, Msg "how are you?") -> c == aliceId; _ -> False
+    ackMessage bob aliceId 2
     3 <- sendMessage bob aliceId "hello too"
     get bob ##> ("", aliceId, SENT 3)
     4 <- sendMessage bob aliceId "message 1"
     get bob ##> ("", aliceId, SENT 4)
     get alice =##> \case ("", c, Msg "hello too") -> c == bobId; _ -> False
+    ackMessage alice bobId 3
     get alice =##> \case ("", c, Msg "message 1") -> c == bobId; _ -> False
+    ackMessage alice bobId 4
     suspendConnection alice bobId
     5 <- sendMessage bob aliceId "message 2"
     get bob ##> ("", aliceId, MERR 5 (SMP AUTH))
@@ -152,6 +156,8 @@ exchangeGreetings alice bobId bob aliceId = do
   1 <- sendMessage alice bobId "hello"
   get alice ##> ("", bobId, SENT 1)
   get bob =##> \case ("", c, Msg "hello") -> c == aliceId; _ -> False
+  ackMessage bob aliceId 1
   2 <- sendMessage bob aliceId "hello too"
   get bob ##> ("", aliceId, SENT 2)
   get alice =##> \case ("", c, Msg "hello too") -> c == bobId; _ -> False
+  ackMessage alice bobId 2