REC handles low volume email marketing, typically up to 2,000 emails per month for a standard licence and is designed for people who have signed up to the site and bought products, rather than importing email addresses from other sources.
For larger email campaigns and mailing out to other email lists we recommend Mailchimp [opens in new tab].
Mailchimp has all the analytical reporting and reputation management tools required for larger mailshots especially where the email addresses come from external email lists.
Warning:
Running email campaigns for imported email addresses through REC can result in reputation damage and cause unwanted server spikes, which is why we limit mailshots in the way we do.