Hi @snicol – a similar question has been answered in the past containing instructions to use the same email to add multiple Customer accounts by adding an alias to the email which might be useful to reference! Check it out here - How to add multiple Businesses entities that have the same Account Administrator?
Other than that, I’m afraid there isn’t a way for the same email to be used twice, as it is considered a unique parameter in our Platform per application.
Please let us know if you have any questions!