I am concerned that my computer has been compromised because I sent an email out - but now I noticed that there is a link in the email I did not insert, and I am worried I have a virus or something. I am seeing an invisible image called cleardot.gif appearing next to the sender's name at the bottom of their email. (immediately to the right after "Sincerely, [their name"]). It only happens with this one person. Where does this come from and what is it?
Here's the HTML code:
<img class="" src="https://mail.google.com/mail/u/0/images/cleardot.gif">