The message should be clear on what Account it is about as based on the information you gave it was likely about your Mozilla Account. This kb article shows what Mozilla Accounts are used for which includes this support.mozilla.org site https://support.mozilla.org/en-US/kb/access-mozilla-services-firefox-account https://support.mozilla.org/en-US/kb/mozilla-account-deletion-inactivity https://support.mozilla.org/en-US/kb/sumo-profile-inactive-deleted The three emails are giving you a heads up to login into your Mozilla Account before a said date so it is not deactivated.