Sending E-mail for Sign in With Apple
Apple’s private email relay server is almost completely undocumented. In this blog post I’ll describe how I got it working.
The key issue is that the “return path” of your emails must be using a subdomain that can be verified by Apple. This blog post from SendGrid describes the solution in detail.
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Upload the apple-developer-domain-association.txt file from Apple to the new subdomain web site. Wait a few extra minutes to make sure the DNS has changed before clicking Verify at Apple.
Previously:
Update (2019-09-25): Curtis Herbert:
For Slopes this is sitting at 75% of users opting to use the email relay.
