Firefox isn't a email program or security program. What kinda email is it that your clicking for it to say that? The browser probably says the link to site is probably unsafe and is being interpreted as a A/V message.

xfinity is my email

This issue can be caused by the presence of mixed passive content like images coming over an open HTTP connection.

You can probably see this in the Web Console. You can hide the CSS messages and leave warnings and error messages.

• "3-bar" menu button or Tools -> Web Developer
• https://developer.mozilla.org/en-US/Tools/Web_Console

You can see a special padlock at the left end of the location/address bar.

• a padlock with a strike through means that mixed active content is blocked
• a padlock with an exclamation mark attached means that mixed passive content (e.g. images) is present, but not blocked

Firefox shows the shield icon at the left end of the location/address bar in case Content Blocking is blocking content.

• click the shield icon for more detail and possibly disable the protection

• https://support.mozilla.org/en-US/kb/mixed-content-blocking-firefox
• https://support.mozilla.org/en-US/kb/content-blocking