The email subject is extremely important. As an average open rate of marketing emails can fluctuate around 20%, the subject is often the only part of the email that is ever read. That’s why you should care about. First, always be specific. Try to express in one short sentence (or better in 4-6 words) the message in the email. Don’t send anything like: “Newsletter 23/2019”. “Free shipping on everything in June!” sounds much better. It could be arduous, but automation could do it for you.
Try to attract the attention with something curious or stunning, but don’t cheat. One of our former clients was somehow a spammer and his by far “the best” email subject was “Our meeting on Friday”, while the email contained a product offer. The open rate was over 80%, but the unsubscribe rate was tremendous as well and people were fed up. But, the customer claimed this still paid off. Nevertheless, using such strategies, expect you will constantly searching for new email service providers.