(EDIT): Left my slightly off-topic comment below as it may be useful to some people anyway; as the two child commenters pointed out, this doesn&#x27;t necessarily relate. It seems as if this was an attack, the non-gmail email must have been compromised as well as I don&#x27;t see a way to turn off these notifications.<p>From what I have seen assisting others with compromised Google accounts (most likely due to a phishing attack, but unconfirmed), emails that would give away the compromise are usually deleted---either manually or via a filter[1].<p>Sometimes these deleted mails can be retrieved because they not purged completely, but deleted mail does not show up in GMail search.<p>[1]: If you believe your account has been compromised, check your email filters, I&#x27;ve seen weird delete filters added to accounts.