Sent from shows old, nonexistent email!

Hello, several years ago I had Thunderbird on an old computer with my then email address of [edited] @sympatico.ca. That email no longer exist. I re-installed Thunderbird on my current computer and setup my new email account. My old, non existent email is NOT one of the email accounts in my Thunderbird. Yet when I click on "send this page" and Thunderbird opens, it shows the "From" email as [edited] @sympatico.ca. There is no drop down menu to select my new and current email address. How do I fix my Thunderbird to select my current, valid email address as the sent "From" address instead of my old non-existent email address? THANK YOU for your help. ''''''''My current email is [edited] @rogers.com''''''''