You can create an arXiv.org account with basically any email address whatsoever[0], with no referral. What you can't necessarily do is upload papers to arXiv without an "endorsement"[1]. Some accounts are given automatic endorsements for some domains (eg, math, cs, physics, etc) depending on the email address and other factors.

Loosely speaking, the "received wisdom" has generally been that if you have a .edu address, you can probably publish fairly freely. But my understanding is that the rules are a little more nuanced than that. And I think there are other, non .edu domains, where you will also get auto-endorsed. But they don't publish a list of such things for obvious reasons.

[0]: Unless things have changed since I created my account, which was originally created with my personal email address. That was quite some time ago, so I guess it's possible changes have happened that I'm not aware of.

[1]: https://info.arxiv.org/help/endorsement.html

Not quite true. If you've got an email associated with a known organization you can submit.

Which includes some very large ones like @google.com