Added POP3 remarks

app/src/main/res/layout/fragment_pop.xml

@@ -513,7 +513,7 @@
             android:id="@+id/cbSummary"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
-            android:layout_marginStart="12dp"
+            android:layout_marginStart="24dp"
             android:layout_marginTop="6dp"
             android:tag="ignore"
             android:text="@string/title_advanced_notify_summary"
@@ -549,15 +549,28 @@
             app:layout_constraintStart_toStartOf="parent"
             app:layout_constraintTop_toBottomOf="@id/cbAutoSeen" />
 
+        <TextView
+            android:id="@+id/tvLeaveServerHint"
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:layout_marginStart="24dp"
+            android:layout_marginTop="6dp"
+            android:text="@string/title_leave_on_server_hint"
+            android:textAppearance="@style/TextAppearance.AppCompat.Small"
+            android:textStyle="italic"
+            app:layout_constraintEnd_toEndOf="parent"
+            app:layout_constraintStart_toStartOf="parent"
+            app:layout_constraintTop_toBottomOf="@id/cbLeaveServer" />
+
         <CheckBox
             android:id="@+id/cbClientDelete"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
-            android:layout_marginStart="12dp"
+            android:layout_marginStart="24dp"
             android:layout_marginTop="12dp"
             android:text="@string/title_client_delete"
             app:layout_constraintStart_toStartOf="parent"
-            app:layout_constraintTop_toBottomOf="@id/cbLeaveServer" />
+            app:layout_constraintTop_toBottomOf="@id/tvLeaveServerHint" />
 
         <CheckBox
             android:id="@+id/cbLeaveDeleted"
@@ -568,6 +581,19 @@
             app:layout_constraintStart_toStartOf="parent"
             app:layout_constraintTop_toBottomOf="@id/cbClientDelete" />
 
+        <TextView
+            android:id="@+id/tvLeaveDeletedHint"
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:layout_marginStart="24dp"
+            android:layout_marginTop="6dp"
+            android:text="@string/title_leave_deleted_hint"
+            android:textAppearance="@style/TextAppearance.AppCompat.Small"
+            android:textStyle="italic"
+            app:layout_constraintEnd_toEndOf="parent"
+            app:layout_constraintStart_toStartOf="parent"
+            app:layout_constraintTop_toBottomOf="@id/cbLeaveDeleted" />
+
         <CheckBox
             android:id="@+id/cbLeaveDevice"
             android:layout_width="wrap_content"
@@ -575,7 +601,20 @@
             android:layout_marginTop="12dp"
             android:text="@string/title_leave_on_device"
             app:layout_constraintStart_toStartOf="parent"
-            app:layout_constraintTop_toBottomOf="@id/cbLeaveDeleted" />
+            app:layout_constraintTop_toBottomOf="@id/tvLeaveDeletedHint" />
+
+        <TextView
+            android:id="@+id/tvLeaveDeviceHint"
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:layout_marginStart="24dp"
+            android:layout_marginTop="6dp"
+            android:text="@string/title_leave_on_device_hint"
+            android:textAppearance="@style/TextAppearance.AppCompat.Small"
+            android:textStyle="italic"
+            app:layout_constraintEnd_toEndOf="parent"
+            app:layout_constraintStart_toStartOf="parent"
+            app:layout_constraintTop_toBottomOf="@id/cbLeaveDevice" />
 
         <TextView
             android:id="@+id/tvMax"
@@ -586,7 +625,7 @@
             android:text="@string/title_max_messages"
             android:textAppearance="@style/TextAppearance.AppCompat.Small"
             app:layout_constraintStart_toStartOf="parent"
-            app:layout_constraintTop_toBottomOf="@id/cbLeaveDevice" />
+            app:layout_constraintTop_toBottomOf="@id/tvLeaveDeviceHint" />
 
         <TextView
             android:id="@+id/tvMaxKeep"

app/src/main/res/values/strings.xml

@@ -1268,9 +1268,12 @@
     <string name="title_primary_identity">Primary (default identity)</string>
     <string name="title_self_identity">Remove email address when replying</string>
     <string name="title_leave_on_server">Leave messages on server</string>
+    <string name="title_leave_on_server_hint">After synchronization, the downloaded messages will remain on the server</string>
     <string name="title_client_delete">Actively delete messages after downloading</string>
     <string name="title_leave_deleted">Leave deleted messages on server</string>
+    <string name="title_leave_deleted_hint">After deleting messages, the messages will remain on the server</string>
     <string name="title_leave_on_device">Leave messages on device</string>
+    <string name="title_leave_on_device_hint">After deleting messages from the server, the messages will remain on the device</string>
     <string name="title_max_messages">Maximum number of messages to download (blank for all)</string>
     <string name="title_max_messages_keep">This is the maximum number of messages that will be kept on the device</string>
     <string name="title_max_messages_remark">