Cresting a new user and email address has been struck through

[Acoma]

Creating a new user the email address has been scribed out, i.e. a line through the enter email address.
I have created other ID's and this has not happened. Under what conditions does the line through the email address happen.
See attached

[yuri]

I believe it's because of this: Administration > System > Mark new email addresses as opted-out.

[Acoma]

All though the Mark new email addresses as opted-out was not ticked, it led me to look at the user in particular, the buttons to the right of the email address when editing have a toggle state that is very hard to distinguish again on and off. and it was the invalid one that was set some how. Toggled that and the strike through has disappeared so the above hint gave me the clue, thank you.