When entering data for testing, it's best to use ones that will never work or ones, that if they're ever used, will result in no real-world effect. This includes using real phone numbers, emails and postal addresses. My tip for emails is to use one on your own domain, eg email@example.com.
This of course may never be an issue, but it's a good habit to get into to be safe rather than sorry.
Heads up: As with any terse bit of advice, there will be exceptions of course, and subtleties and nuance that can't possibly be captured in a Byte of Wisdom. This has been what I've experienced, I'd love to hear yours in the comments too!
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