diff --git a/app/src/main/kotlin/com/tutpro/baresip/Account.kt b/app/src/main/kotlin/com/tutpro/baresip/Account.kt
index a10ad8ac..105ded9d 100644
--- a/app/src/main/kotlin/com/tutpro/baresip/Account.kt
+++ b/app/src/main/kotlin/com/tutpro/baresip/Account.kt
@@ -28,6 +28,7 @@ class Account(val accp: Long) {
     var dtmfMode = Api.account_dtmfmode(accp)
     var answerMode = Api.account_answermode(accp)
     var autoRedirect = Api.account_sip_autoredirect(accp)
+    var blockUnknown = false
     var vmUri = Api.account_vm_uri(accp)
     var vmNew = 0
     var vmOld = 0
@@ -72,6 +73,7 @@ class Account(val accp: Long) {
         if (Utils.paramExists(extra, "regint"))
             configuredRegInt = Utils.paramValue(extra, "regint").toInt()
         callHistory = Utils.paramValue(extra, "call_history") == ""
+        blockUnknown= Utils.paramExists(extra, "block_unknown")
         if (Utils.paramExists(extra, "country_code"))
             countryCode = Utils.paramValue(extra, "country_code")
         if (Utils.paramExists(extra, "tel_provider"))
@@ -148,6 +150,9 @@ class Account(val accp: Long) {
         if (autoRedirect)
             res += ";sip_autoredirect=yes"
 
+        if (blockUnknown)
+            res += ";block_unknown=yes"
+
         res += ";ptime=20;regint=${regint};regq=0.5;pubint=0;inreq_allowed=yes;call_transfer=yes"
 
         var extra = ""
diff --git a/app/src/main/kotlin/com/tutpro/baresip/AccountScreen.kt b/app/src/main/kotlin/com/tutpro/baresip/AccountScreen.kt
index 39f0f265..52c3fee4 100644
--- a/app/src/main/kotlin/com/tutpro/baresip/AccountScreen.kt
+++ b/app/src/main/kotlin/com/tutpro/baresip/AccountScreen.kt
@@ -966,6 +966,31 @@ private fun AccountContent(
         }
     }
 
+    @Composable
+    fun BlockUnknown() {
+        val block by viewModel.blockUnknown.collectAsState()
+        Row(
+            Modifier.fillMaxWidth().padding(end = 10.dp),
+            verticalAlignment = Alignment.CenterVertically,
+            horizontalArrangement = Arrangement.Start
+        ) {
+            Text(text = stringResource(R.string.block_unknown),
+                modifier = Modifier
+                    .weight(1f)
+                    .clickable {
+                        alertTitle.value = ctx.getString(R.string.block_unknown)
+                        alertMessage.value = ctx.getString(R.string.block_unknown_help)
+                        showAlert.value = true
+                    },
+                fontSize = 18.sp
+            )
+            Switch(
+                checked = block,
+                onCheckedChange = { viewModel.blockUnknown.value = it }
+            )
+        }
+    }
+
     @Composable
     fun Voicemail() {
         val vmUri by viewModel.vmUri.collectAsState()
@@ -1142,6 +1167,7 @@ private fun AccountContent(
         Dtmf()
         Answer()
         Redirect()
+        BlockUnknown()
         Voicemail()
         CountryCode()
         TelProvider()
@@ -1449,6 +1475,12 @@ private fun checkOnClick(ctx: Context, viewModel: AccountViewModel, ua: UserAgen
         Log.d(TAG, "New autoRedirect is ${acc.autoRedirect}")
     }
 
+    val newBlockUnknown = viewModel.blockUnknown.value
+    if (newBlockUnknown != acc.blockUnknown) {
+        acc.blockUnknown = newBlockUnknown
+        Log.d(TAG, "New blockUnknown is ${acc.blockUnknown}")
+    }
+
     var newVmUri = viewModel.vmUri.value.trim()
     if (newVmUri != acc.vmUri) {
         if (newVmUri != "") {
diff --git a/app/src/main/kotlin/com/tutpro/baresip/AccountViewModel.kt b/app/src/main/kotlin/com/tutpro/baresip/AccountViewModel.kt
index 4c818ae9..23f8325f 100644
--- a/app/src/main/kotlin/com/tutpro/baresip/AccountViewModel.kt
+++ b/app/src/main/kotlin/com/tutpro/baresip/AccountViewModel.kt
@@ -23,6 +23,7 @@ class AccountViewModel: ViewModel() {
     val dtmfMode = MutableStateFlow(0)
     val answerMode = MutableStateFlow(0)
     val autoRedirect = MutableStateFlow(false)
+    val blockUnknown = MutableStateFlow(false)
     val vmUri = MutableStateFlow("")
     val countryCode = MutableStateFlow("")
     val telProvider = MutableStateFlow("")
@@ -54,6 +55,7 @@ class AccountViewModel: ViewModel() {
         dtmfMode.value = acc.dtmfMode
         answerMode.value = acc.answerMode
         autoRedirect.value = acc.autoRedirect
+        blockUnknown.value = acc.blockUnknown
         vmUri.value = acc.vmUri
         countryCode.value = acc.countryCode
         telProvider.value = acc.telProvider
diff --git a/app/src/main/kotlin/com/tutpro/baresip/BaresipService.kt b/app/src/main/kotlin/com/tutpro/baresip/BaresipService.kt
index c6f6f758..565b4716 100644
--- a/app/src/main/kotlin/com/tutpro/baresip/BaresipService.kt
+++ b/app/src/main/kotlin/com/tutpro/baresip/BaresipService.kt
@@ -850,34 +850,38 @@ class BaresipService: Service() {
                     "incoming call" -> {
                         val peerUri = ev[1]
                         val bevent = ev[2].toLong()
-                        val toastMsg = if (!Utils.checkPermissions(this, arrayOf(RECORD_AUDIO)))
+                        val blockUnknown = ua.account.blockUnknown && Contact.contactName(peerUri) == peerUri
+                        val toastMsg = if (Call.inCall() || blockUnknown)
+                            String.format(getString(R.string.call_auto_rejected),
+                                Utils.friendlyUri(this, peerUri, ua.account))
+                        else if (!Utils.checkPermissions(this, arrayOf(RECORD_AUDIO)))
                             getString(R.string.no_calls)
                         else if (!requestAudioFocus(applicationContext))
                             // request fails if there is an active telephony call
                             getString(R.string.audio_focus_denied)
-                        else if (Call.inCall())
-                            String.format(getString(R.string.call_auto_rejected),
-                                Utils.friendlyUri(this, peerUri, ua.account))
                         else
                             ""
                         if (toastMsg != "") {
-                            Log.d(TAG, "Auto-rejecting incoming call $uap/$peerUri")
+                            Log.d(TAG, "Auto-rejecting incoming call to $uap from $peerUri")
                             Api.sip_treply(callp, 486, "Busy Here")
                             Api.bevent_stop(bevent)
                             toast(toastMsg)
-                            val name = "callwaiting_$toneCountry"
-                            val resourceId = applicationContext.resources.getIdentifier(
-                                name,
-                                "raw",
-                                applicationContext.packageName)
-                            if (resourceId != 0) {
-                                playUnInterrupted(resourceId, 1)
-                            } else {
-                                Log.e(TAG, "Callwaiting tone $name.wav not found\")")
-                            }
-                            if (ua.account.callHistory) {
-                                CallHistoryNew(aor, peerUri, "in").add()
-                                ua.account.missedCalls = true
+                            if (!blockUnknown) {
+                                val name = "callwaiting_$toneCountry"
+                                val resourceId = applicationContext.resources.getIdentifier(
+                                    name,
+                                    "raw",
+                                    applicationContext.packageName
+                                )
+                                if (resourceId != 0) {
+                                    playUnInterrupted(resourceId, 1)
+                                } else {
+                                    Log.e(TAG, "Callwaiting tone $name.wav not found\")")
+                                }
+                                if (ua.account.callHistory) {
+                                    CallHistoryNew(aor, peerUri, "in").add()
+                                    ua.account.missedCalls = true
+                                }
                             }
                             return
                         }
@@ -1207,6 +1211,18 @@ class BaresipService: Service() {
             return
         }
 
+        if (ua.account.blockUnknown && Contact.contactName(peerUri) == peerUri) {
+            Log.d(TAG, "Auto-rejecting incoming message by $uap from $peerUri")
+            toast(String.format(
+                    getString(R.string.message_auto_rejected),
+                    Utils.friendlyUri(this, peerUri, ua.account)
+                )
+            )
+            // Api.sip_treply(callp, 486, "Busy Here")
+            // Api.bevent_stop(bevent)
+            return
+        }
+
         val charsetString = Utils.paramValue(cType.replace(" ", ""), "charset")
         val charset = try {
             Charset.forName(charsetString)
diff --git a/app/src/main/res/values-fi/strings.xml b/app/src/main/res/values-fi/strings.xml
index bb745032..bbcb2f24 100644
--- a/app/src/main/res/values-fi/strings.xml
+++ b/app/src/main/res/values-fi/strings.xml
@@ -207,6 +207,8 @@
     <string name="answer_mode_help">Valitsee tulevien puheluiden vastaustavan.</string>
     <string name="manual">Manuaalinen</string>
     <string name="auto">Automaattinen</string>
+    <string name="block_unknown">Estä tuntemattomat</string>
+    <string name="block_unknown_help">Estä puhelut ja viestit, joiden lähdettä ei löydy yhteystiedoista.</string>
     <string name="redirect_mode">Uudelleenohjaustapa</string>
     <string name="redirect_mode_help">Valitsee toteutetaanko puhelun uudelleenohjauspyyntö
         automaattisesti vai kysytäänkö vahvistusta.</string>
@@ -543,9 +545,9 @@
     <string name="call_failed">Puhelu epäonnistui</string>
     <string name="call_closed">Puhelu on päättynyt</string>
     <string name="call_not_secure">Tämä puhelu EI ole turvallinen!</string>
-    <string name="peer_not_verified">Tämä puhelu on turvallinen, mutta kohdetta ei ole
+    <string name="peer_not_verified">Tämä puhelu on turvallinen, mutta puhelun toista osapuolta ei ole
         todennettu!</string>
-    <string name="call_is_secure">Tämä puhelu on turvallinen ja kohde on
+    <string name="call_is_secure">Tämä puhelu on turvallinen ja puhelun toinen osapuoli on
     todennettu! Haluatko poistaa todennuksen\?</string>
     <string name="unverify">Poista todennus</string>
     <string name="backed_up">Sovelluksen tiedot (äänityksiä lukuunottamatta)
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index 15397fa6..fd93ed61 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -201,6 +201,8 @@
         if confirmation is requested.</string>
     <string name="manual">Manual</string>
     <string name="auto">Automatic</string>
+    <string name="block_unknown">Block Unknown</string>
+    <string name="block_unknown_help">Block calls and messages from peers that are not found in contacts.</string>
     <string name="voicemail_uri">Voicemail URI</string>
     <string name="voicemain_uri_help">SIP URI for checking of voicemail messages. If left empty, voicemail
         messages (Message Waiting Indications) are not subscribed to.
@@ -248,6 +250,7 @@
     <string name="missed_calls_count">%1$d missed calls</string>
     <string name="transfer_request_to">Call transfer request to</string>
     <string name="call_auto_rejected">Auto-rejected call from \`%1$s\`</string>
+    <string name="message_auto_rejected">Auto-rejected message from \`%1$s\`</string>
     <!-- Calls Activity -->
     <string name="call_history">Call History</string>
     <string name="call_details">Call Details</string>