Right now, look at statistics analysis in the e-mail newsletter service to understand why people unsubscribe from receiving emails. There is a banal advice, but in practice it is often forgotten, although this step will help to immediately identify the problem and take measures to remedy the situation. If you don’t use test email addresses in your newsletter, it's time to start doing this - maybe some clients just don’t receive messages. There are not so many mail services, get accounts in each and include these addresses in the database. After each mailing check to see if the letters reached the addressees. Analyze which letters customers receive automatically. For example, a welcome letter - its text is important. If a person has subscribed to the newsletter, thank him not only in words, but indeed, by making a really good offer. And immediately give an idea to add your e-mail address to the clients’ address book, so that they do not miss other interesting offers. Just write: “do not miss the benefits in the future - add this email to your address book”. From this point on, start working only on increasing the loyalty of your customers – put away promotional letters, because there is always something more useful your business professionals can tell their subscribers.