What does a 'blue line' across an email mean?

site · February 25

I get a 'blue line' from left to right across certain emails, when I click on it it disappears. This line appears mostly on bank emails or purchase emails. When I get the email Bitdefender notifies me in a small window 'Suspicious Activity', that the email is not directed where it should be. I know at one point my passwords were compromised & my emails were affected. I am doing everything within my capability to find out how/who is doing this.