#9559: Don't call _pre_mailbox_hook more than once
diff --git a/Lib/mailbox.py b/Lib/mailbox.py
index 8d3f8b6..73c43e2 100644
--- a/Lib/mailbox.py
+++ b/Lib/mailbox.py
@@ -740,8 +740,11 @@
"""Append message to mailbox and return (start, stop) offsets."""
self._file.seek(0, 2)
before = self._file.tell()
- if len(self._toc) == 0:
- # This is the first message
+ if len(self._toc) == 0 and not self._pending:
+ # This is the first message, and the _pre_mailbox_hook
+ # hasn't yet been called. If self._pending is True,
+ # messages have been removed, so _pre_mailbox_hook must
+ # have been called already.
self._pre_mailbox_hook(self._file)
try:
self._pre_message_hook(self._file)