When it comes to deciding how to craft that perfect subject line, there appears to be really only one area to avoid: the subject line of 60 to 70 characters. Marketers refer to this as the “dead zone” of subject length. According to research by Adestra, which tracked over 900 million emails for its report, there is no increase in either open rate or clickthroughs at this 60-to-70 character length of subject line.
Discussion lists often require every message to be approved by a moderator before being sent to the rest of the subscribers (moderated lists), although higher-traffic lists typically only moderate messages from new subscribers. Companies sending out promotional newsletters have the option of working with whitelist mail distributors, which agree to standards and high fines from ISPs should any of the opt-in subscribers complain. In exchange for their compliance and agreement to prohibitive fines, the emails sent by whitelisted companies are not blocked by spam filters, which often can reroute these legitimate, non-spam emails.[11]

Bloggers are the most obvious example of focusing on this email marketing strategy almost exclusively. SaaS (Software as a Service) businesses are another group that typically heavily emphasize content emails. Of course, bloggers, SaaS businesses, and everyone else can send content emails while also using the other email marketing strategies. And you should do it, too.
Win-back: An existing customer is soon approaching the end of his yearly subscription. The customer hasn’t used your product in 3 months and you need a way to win them back and keep them for another year. Create a “win back” email that sends an automated email to all customers that are coming to end of their contract with a list of new product features and a short plan on expected releases in the next six months.

Take advantage of the email template designer or upload your own. There are also tools to segments lists and personalize emails with all your contact data. The A/X testing feature allows you to test up to ten different versions of your email before you decide which one stands out as the best. A campaign comparison tool pits your previous campaigns against the current one to give a complete picture.
Keep the subject line and pre-header short: The subject line is crucial. Keep it short so the reader knows exactly what the email topic is about. And the pre-header text (also known as snippet text), don’t let it go to waste by using “To view this email in your browser…”. Instead, summarize the email or include a call to action (i.e., Use “FREESHIP” to get free shipping).