There is an auto-complete address in my email address box and it prevents me from typing in the correct address
I cut-and-pasted an email address that I wanted to use. It showed up in red in my email address "to" box. When I tried to send that email, the email app said there was no address there. I tried to delete the address-in-red and type in the address by hand, but the address keeps on changing to being covered in red and the app keeps on saying there is no address there.
Could be Firefox's autocomplete feature. Are you able to remove the suggestion by selecting it (using the down arrow-key on your keyboard) and then hitting the delete key?