[tony101]

Exactly. Wouldn't this be a good way to harvest a ton of valid email addresses?

[amnah]

This was my first thought. I definitely wouldn't risk my client's privacy going through a third party like this.

[pmontra]

I usually seed dev and test databases with fake data. Emails are usually a sequence like [e-mail] 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.