I usually seed dev and test databases with fake data. Emails are usually a sequence like userN@example.com
Sending mail to that is usually not a problem, unless the content of the mail is somewhat sensitive. Again, fake data helps. When I work with Ruby I use the faker gem.
If you have to import production data then, yes, that would be annoying. Anonimizing data sometimes is not easy.
If you have to import production data then, yes, that would be annoying. Anonimizing data sometimes is not easy.