diff --git a/domain/src/main/java/com/moez/QKSMS/util/Preferences.kt b/domain/src/main/java/com/moez/QKSMS/util/Preferences.kt
index debc976b31de6a2821c227b8f4cc36a5d023d71f..b9aa930324b0b283ff662c42d263523efb85b9f4 100644
--- a/domain/src/main/java/com/moez/QKSMS/util/Preferences.kt
+++ b/domain/src/main/java/com/moez/QKSMS/util/Preferences.kt
@@ -120,7 +120,7 @@ class Preferences @Inject constructor(
     val mobileOnly = rxPrefs.getBoolean("mobileOnly", false)
     val autoDelete = rxPrefs.getInteger("autoDelete", 0)
     val longAsMms = rxPrefs.getBoolean("longAsMms", false)
-    val mmsSize = rxPrefs.getInteger("mmsSize", 300)
+    val mmsSize = rxPrefs.getInteger("mmsSize", -1)
     val logging = rxPrefs.getBoolean("logging", false)
 
     init {
diff --git a/presentation/src/main/java/com/moez/QKSMS/feature/main/MainActivity.kt b/presentation/src/main/java/com/moez/QKSMS/feature/main/MainActivity.kt
index 06ab61d5b1b18bc258a507d3f312589cd7802447..aad641a4f3a48bcddac19fde8725d075d4669936 100644
--- a/presentation/src/main/java/com/moez/QKSMS/feature/main/MainActivity.kt
+++ b/presentation/src/main/java/com/moez/QKSMS/feature/main/MainActivity.kt
@@ -23,8 +23,10 @@ import android.animation.ObjectAnimator
 import android.app.AlertDialog
 import android.content.Intent
 import android.content.res.ColorStateList
+import android.content.SharedPreferences
 import android.os.Build
 import android.os.Bundle
+import android.preference.PreferenceManager
 import android.view.Gravity
 import android.view.Menu
 import android.view.MenuItem
@@ -179,6 +181,22 @@ class MainActivity : QkThemedActivity(), MainView {
         if (Build.VERSION.SDK_INT <= 22) {
             toolbarSearch.setBackgroundTint(resolveThemeColor(R.attr.bubbleColor))
         }
+
+        val sharedPreferences: SharedPreferences =
+            PreferenceManager.getDefaultSharedPreferences(this)
+        val editor: SharedPreferences.Editor = sharedPreferences.edit()
+        var changeDefault: Int = sharedPreferences.getInt("changeDefault", 0)
+        when (changeDefault) {
+            0 -> {
+                // Set MMS site auto (-1) if its 300kb
+                val mmsSize: Int = sharedPreferences.getInt("mmsSize", 300)
+                if (mmsSize == 300) {
+                    editor.putInt("mmsSize", -1)
+                }
+                changeDefault++
+            }
+        }
+        editor.putInt("changeDefault", changeDefault).apply()
     }
 
     override fun onNewIntent(intent: Intent?) {
diff --git a/presentation/src/main/res/values/strings.xml b/presentation/src/main/res/values/strings.xml
index ac330d353ba370a816d33398e1745d4fc4ca4fb5..7351432965826f0769cf54e00b8ae5baca54b4a6 100644
--- a/presentation/src/main/res/values/strings.xml
+++ b/presentation/src/main/res/values/strings.xml
@@ -457,7 +457,7 @@
     </string-array>
 
     <string-array name="mms_sizes">
-        <item>Automatic</item>
+        <item>Automatic (uses allowed carrier max size)</item>
         <item>100KB</item>
         <item>200KB</item>
         <item>300KB</item>