First, make sure you are hitting inbox. If you followed an ideal warming plan (you didnt get your domain or IPs blacklisted), you should have a baseline of performance to measure against. IE if your average open rate hovers around 5% within a one hour window from send, your performance should not deviate much from this during the span of the send. If you see little to no open rate during your send, you are either bouncing out at the server level or hitting junk. Ideally, pause your campaign and inject some active users (openers/ clickers) and resume; this will help increase your positive engagement. The algorithms want to see people opening, clicking, replying, moving from junk to inbox, marking as "important", adding to the address book, and so forth. These are positives that will help ensure your delivery. Lack of these metrics or high negatives (unsubs, bounces, mark as spam) will hurt your sender rep and defer you to junk or bounce out. I always start here because some do not realize that most of their mailings are bouncing them into the banned sender space. Also, split your sends by inbox provider IE one list for aol, one for gmail, one for msn, one for yahoo, etc. This will allow you to see how you are performing at each ISP and tweak accordingly.
Second, manage your HTML well. Keep your HTML to text ratios balanced. Do not send single images as the message. Big red flag. Ideally, you want much more text than images in your HTML. Also, never send something the rest of the world is already sending (see affiliate network creative). If you are in the space of sending emails with offers only, brand your emails and create your own unique collateral. Never send content that you know other mailers are sending. This is a guarantee poop the bed scenario. Work with the network and create your own offers (your own landing page/ domain, your own HTML, etc). A good email marketing affiliate network will let you send creative to their legal resource for approval. Once approved, do not share this creative. Shared creative is usually cloudmarked and you will get bounced out for poor content. When you build your own creative, render test it. Create an email account at every major inbox provider (gmail, aol, msn, yahoo). Send test emails to these addresses and see how they look in each inbox (mobile and web). If they are not rendering properly in each environment, tweak the code until they do. Dumpy looking emails will hurt your engagement.
Third, mirror high quality. If you know of a company or an individual killing it in your space, sign up for their emails. If they are good at what they do, follow their trends. Analyze the types of messages they send from the welcome, to the daily, to the hyper engaged segments (click on their emails to see if you get follow ups). Mirror their content and send patterns. Likely, if they are successful, they have already A/B tested their best content and subject lines since day one. Check out what they send, when, to whom, and semi-copy what they do (but create your own version).
Fourth, always A/B test. Ideally, take 10% of your list on every send A/B test the subject lines and creative before the full send. Be sure to not deviate too much in what you test or else your results will be inconclusive. Send the balance audience of your test which version performed higher; this makes more of a difference than people realize. Try and do this for every send. It is more work, but it makes a difference.
