This problem is not computer dependant as I've tried it on a couple of computers (mine and friends').
Since some time ago when I log into Yahoo Mail and want to compose a new email, when I'm typing in the recipient's email address this happens:
So what exactly happened in this case is this: I wrote i, n, f, o and @. And after the "@" the line gets that weird red outlining and I am unable to continue writing down the desired email address. So the @ sign basically breaks the whole thing.
For now I'm writing down email addresses in the email "Body" and then copying them as whole into the "To:" to be able to send mails. Has anyone any clue what this is all about and how to fix it?