GMail messages are vulnerable to interception.
An attacker has only to transmit malformed test messages to himself,
and information left over in memory,
from previous messages destined for other people,
will appear with the test messages, in the attacker's inbox.
Sometimes, this information may include usernames and passwords...
Gmail maybe knew the problem and made some change.
I worte a malformed (From: <test@test.com) message to myself,
Click the message shows:
Oops...the system was unable to perform your operation.
Please try again in a few seconds