Email services provider Silverpop's study, "Email Creative That Works," confirms some commonly held beliefs - and offers a few surprises, too - regarding email marketing best practices.

Branding in the subject line is critical, improving open rates 32-60 percent, writes Internet Retailer, citing the Silverpop study of B2B and B2C emails. Lifestyle photography results in higher click rates for B2C emails - but lower rates for B2B. Though the postcard design is popular with B2C email marketers, the newsletter-style copy and format produces higher click rates.

Moreover, Silverpop found that too many links - usually around 6 to 10 in an email message - result in a lower numbers of clicks. Also, although B2C marketing email promotions more often feature a percentage off purchase price, dollar amounts off generate more clicks.

"Click rates for emails offering a specific dollar amount off were 45 percent higher than those offering a percent discount," according to the study.