• Litmus PutsMail –– test your HTML emails before sending them using this service.
• Email on Acid –– email pre-deployment checklist and a configurable part of your email marketing campaign.
• Preview My Email –– preview your email before sending the campaign and increase click rates.
• HTML Email Check –– check the markup (HTML, XHTML, CSS) of HTML emails and newsletters before you send.
• MailNinja –– preview and check your HTML email marketing campaigns and templates. 100% free tool.