A web-based interface is often available to allow people to subscribe, unsubscribe, and change their preferences. However, mailing list servers existed long before the World Wide Web, so most also accept commands over email to a special email address. This allows subscribers (or those who want to be subscribers) to perform such tasks as subscribing and unsubscribing, temporarily halting the sending of messages to them, or changing available preferences - all via email. The common format for sending these commands is to send an email that contains simply the command followed by the name of the electronic mailing list the command pertains to. Examples: subscribe anylist or subscribe anylist John Doe.
No matter how effective the subject line you’ll always have subscribers who don’t open it for a variety of reasons. Send your email again specifically targeting a list segment of those who didn’t open the first time around. Not only is this a second chance in case they just missed the first email, it’s another opportunity to further split test subject lines as well as send times.
In dividing your list in this manner, you give yourself the ability to send more targeted communication. Some customers want both product and sales updates, while others might only want to hear about new versions. If you don’t give them the chance to choose, you risk losing them all-together. Since customers make the best buyers, it’s fairly obvious why you want to keep them subscribed to your customer email list.
Your email list, on the other hand, is yours, free and clear. Using your website and social media to attract visitors and followers, and then encouraging them to sign up for your email list gives you the opportunity to contact your prospects at any point in the future, with any kind of messaging you want; and you’re not bound by search engine rankings or social media algorithms.