First you decide what source of emails you want boosted:
Plain-text and HTML
Then Email Booster will:
Analyze your email Subject and tell you how to improve it. It even checks against a massive database of words that can either help or hurt your conversions.
Make sure your email Body is up-to-snuff with no bad code, enough content to not be flagged as Spam, and contains a mailing address (also less likely to be Spam)
Check that your hyperlinks are valid.
Scan your email with SpamAssassin (the best spam-prevention tool out there).
Ensure your images are as optimized as possible and contain proper descriptors (in case they can't be loaded in an email client).
About Campaign Monitor
With Campaign Monitor, you can easily attract new subscribers by sending them beautiful email newsletters. Built from the ground up for creative professionals, you can manage all your clients from a single account and let them send campaigns at prices you set.
MailChimp is an email marketing service provider with more than 7 million users worldwide who send some 10 billion emails through the service each month.
MailChimp allows its users to design great looking email newsletters through a wide range of different templates and drag-and-drop features. Once newsletters have been designed and filled with content, MailChimp allows its users to send their newsletters, manage subscriber lists, and track campaign performance.
MailChimp offers a variety of plug-ins for other programs and integrates with many systems such as PayPal, Shopify, Google Analytics, Salesforce, etc.