hi, mozilla is relying on google's website classifications to provide that service which should be blocking malicious links/sites. unfortunately this url seems to got flagged by google: https://www.google.com/transparencyreport/safebrowsing/diagnostic/#url=https://3c-lxa.mail.com/ please contact the support of your mail-provider about this issue. hopefully they can resolve the issue together with google. thank you for your understanding!