Don't call open() from RealImapFolder.appendMessages()

mail/protocols/imap/src/main/java/com/fsck/k9/mail/store/imap/RealImapFolder.kt

@@ -964,7 +964,6 @@ internal class RealImapFolder(
      */
     @Throws(MessagingException::class)
     override fun appendMessages(messages: List<Message>): Map<String, String>? {
-        open(OpenMode.READ_WRITE)
         checkOpen()
 
         return try {

mail/protocols/imap/src/test/java/com/fsck/k9/mail/store/imap/RealImapFolderTest.kt

@@ -994,6 +994,19 @@ class RealImapFolderTest {
         assertThat(buffer.readUtf8()).isEqualTo("text")
     }
 
+    @Test
+    fun `appendMessages() on closed folder should throw`() {
+        val folder = createFolder("Folder")
+        val messages = listOf(createImapMessage("1"))
+
+        assertFailure {
+            folder.appendMessages(messages)
+        }.isInstanceOf<MessagingException>()
+            .hasMessage("Folder Folder is not open.")
+
+        verifyNoMoreInteractions(imapConnection)
+    }
+
     @Test
     fun appendMessages_shouldIssueRespectiveCommand() {
         val folder = createFolder("Folder")