FIX UPDATE
An update for anyone who stumbles across this issue – I installed the MandrillWP plugin and setup an account on their website which has fixed this.
Thanks for your response – I am hosting the site on my own hosting account though the domain is done via the client/restaurant’s own domain account (they own multiple). Any guidance as to what I can do to mark it as not-spam would be great!
thanks again! deleted all wp files, reinstalled and started from scratch making sure the wp site was setup as domain.com and not https://www.domain.com and it works!
UPDATE: Just noticed when i open the Network Setup page, it says:
Registration and support emails will come from this address. An address such as [email protected]