Our developer has suggested the following:
For the easiest possible config, I’d recommend the following: Set up an account whose sole purpose is for WordPress to send emails, set this as the admin email for the installation (Dashboard > Network Admin > Settings), and then whitelist all emails coming from this address.
There’s another more complicated option, but just in case you need to explore this possibility:
If a campus is experiencing problems with WP emails being marked as spam, especially outside of the institution, it’s probably because the server is not properly configured to be an email sender. This setup requires some dark magic like reverse DNS, so I’d recommend using an SMTP plugin that will offload the sending process onto a proper email server.
I hope this helps! And please let me know if you have any more questions about the configuration in Network Settings.