Using LMDE fully updated.
I ran into this yesterday for the first time. Seems like a reasonable idea, but in my case the incorrect password was nothing more than a case of fat fingers. I was surprised to receive a system email with only one failed attempt. I can better understand an email with, say, three straight failed attempts. Is there a way to disable system mails when an incorrect password is used with the Update Manager? I do not see anything in the Update Manager Preferences.