Delete row from workbook 1 if value exists in workbook 2

Hi there,
I've never created any Macros/VBscripts before, so I started by googling what I need to do and found a couple of useful resources but not really knowing enough I was unable to make any changes to do exactly what I need so I've come here to find some more help.

I have a supplied list of users with email addresses in column A. This workbook has a single sheet.

I also have a reference list of opted-out users I need to exclude, the email addresses exist in Column A here too, however there are multiple sheets and the user can exist on one or more (or none) sheets.

I need to run the script in the supplied file to delete any rows if the email address in Column A matches anywhere in all sheets of the reference file.

Can anyone point me in the right direction? All the answers I've found refer to single sheets in two workbooks or to two sheets in the same workbook.

Thanks everyone.
Gav

Can anyone help?