I have had to deal with so many customers unable to receive their account activation email when using an educational, government, or outlook account. The Shopify support docs say
If your customers or staff aren't receiving email notifications, then tell them to check their spam or junk folder. If the problem persists, ask them to supply an alternate email address using a different email provider.
But if the customer has made purchases or has a subscription attached to that email, you can't just tell them to try a different email. Plus that's a terrible user experience when you're trying to convert customers to have accounts. I feel like Shopify should try to fix this. Here are some of the errors I see from rejected emails:
Spectrum.net - 1160 - 1190 - The email you tried to send goes against your domain’s security policies. Please contact the email administrators of your domain.
centurylink.net - 550 - Domain [domainname] does not designate [ip address] as permitted sender (in reply to MAIL FROM command).
mx.xtra.co.nz - 550 - Message rejected due to SPF policy (in reply to end of DATA command).
I see these errors over and over again with account activations. Please help Shopify.