Constant error messages popping up - PLEASE HELP

[mbillie1]

so I keep getting these things, at first it was one-at-a-time until I closed it, now it's 3-at-a-time and they replenish instantly when I close them, they appear to think that I'm sending spam (??) and there is nothing in the "sent" section of my email client... what do I do here? I'm running Norton AntiVirus right now but oh my god I'm about to just smash my computer into a million pieces