diff --git a/iarchiver/mail_conn.py b/iarchiver/mail_conn.py
index e4fa83c..861e4eb 100644
--- a/iarchiver/mail_conn.py
+++ b/iarchiver/mail_conn.py
@@ -130,7 +130,7 @@ class MailConnection:
         """
         if not search_criterion:
             search_criterion = ['ALL']
-        self.mail.select(normalize_for_imap_folder(folder))
+        self.mail.select(normalize_for_imap_folder(folder), readonly=True)
         for search_item in search_criterion:
             result, data = self.mail.uid('search', search_item)
             mail_ids = data[0]