Putting it out there to solve a problem which has blighted me for some years now.
Once upon a time, i entered my email address wrong in a form in Safari.
Now I get a little blue text pop-up having a close X to the right with my wrong email address (it happens to be missing the first letter of my first name). If I type the @ symbol, then it kindly fills in my wrong email address. I have to click the X to dismiss this pop-up, and then Autofill kindly does the domain.com bit for me.
Here's (hopefully) an image of the problem in action:
It should be simple to fix by googling the right term and following some clear instructions, if only I knew what it was called.
I've done the usual things like making sure Autofill (Safari/Preferences/Autofill) is using the correct Contacts card for me, and this helps to a degree in that Autofill will then prompt me to enter the correct email address.
I even tried using System Preferences>Keyboard>Text to create a system wide substitution preference, but this sadly doesn't work.
And the real killer, it has somehow followed me for several years from Mac to Mac, which makes me think it is linked to an iCloud setting or preference.
If you know what it's called and can point me at a fix, I'll be very grateful.