diff --git a/backup_imap/backup_imap.py b/backup_imap/backup_imap.py
index 8e07c22..e9e567f 100644
--- a/backup_imap/backup_imap.py
+++ b/backup_imap/backup_imap.py
@@ -68,7 +68,7 @@ class BackupImap:
         if mailbox == '':
             real_mailbox = 'INBOX'
         else:
-            real_mailbox = mailbox.encode()
+            real_mailbox = mailbox
         self.imap.select(mailbox=f"\"{real_mailbox}\"", readonly=False)
         self._log.debug(
             "Searching for all messages in '%s'...",
@@ -100,6 +100,14 @@ class BackupImap:
                 msg_counter += 1
                 fetch_response, fetch_data = self.imap.fetch(message_uid, "(RFC822)")
                 if fetch_response == 'OK':
+                    store_result, unseen_data = self.imap.store(message_uid, '-FLAGS', '\\Seen')
+                    if store_result != 'OK':
+                        self._log.error(
+                            "Error marking as unseen the message '%s'. %s",
+                            message_uid,
+                            unseen_data
+                        )
+                        sys.exit(6)
                     subject = f'__no_subject__{message_uid}'
                     data = fetch_data[0][1]
                     subject_match = re.search(rb'Subject: (.*)\r\n', data)