If you are having a higher unsubscribing rate and you are not sure what wrong has happened, then you should take a look at these reasons why you might be disengaging your subscribers:
Stop Following - If you are delivering out everyday emails or even more than one email per day (yes… some organizations do) then you will possibly frustrate your subscriber by mentioning his name every time ! Nobody can have that much to say about their company all of enough time so keep in mind, less is more. Once per weeks time or once monthly is probably adequate to get your message across and make it exciting and attractive. You need to make it sure that you should attract the attention of people because people are generally overwhelmed with emails.
Live up to expectation - Probably you have crafted the most tempting subject lines but if your message doesn’t live up to the expectation then you are going to let your subscribers. Usually people will hit the unsubscribe button if you are not offering anything useful or at the very least, interesting for them. This implies exciting, useful content and if you haven't got enough time, know how or tendency to create it, then get a content writer in! Expectation + Frustration = Unsubscribe. It is as simple as that.
Hype - You might think that your offer is the best thing since digital watch but if you keep pushing it down to the people’s throats with recurring call to actions using terminology such as 'for a limited time only' and 'act now' then people will think you're a bit of a 'Del boy' and eventually disengage. Try a bit of delicacy…
Inconsistency - If there is one more awful than delivering too many emails, that is sending emails inconsistently. If you said in the beginning that you would deliver a weekly/monthly update, then do that. Don't do it when you prefer to send it. People generally will have more assurance with you and begin to interact with with you if you have a regular conversation with them and you show that you are man of your word.
Design - Lack of proper designing, poor layout, broken images and links, unsupported design for mobile devices, lack of branding etc these are all reasons that will make people reaching to the unsubscribe link. While it is attractive to use free email templates, but think about dealing with a company who knows that it is eventually the mixture of great style and excellent layout that will get you attention.