A necessary step before sending an email campaign or newsletter. Many email clients permit you to send a test email before sending a regular email newsletter or solo mailing, in which you would send one copy of the message to an in-house email address and then review it for formatting or copy errors or improperly formatted links. Email marketers should also send a test campaign to a list of email addresses not in the deployment database to determine likely response rates and how well different elements in the message perform.