Some amount of unsubscribes is normal for a list, but there are definitely things that you can do to make sure that you aren't losing more subscribers than you have to.
Here are three major factors that often affect the decision to unsubscribe:
Sending frequency is an important factor to consider when you are looking into the reasons that your subscribers are leaving - too many messages can definitely be a problem, but so can too few - try to strike a balance.
If subscribers are seeing something like this. . .
. . .it should be obvious there is a problem. Eight messages in the space of three days is just too many. A subscriber seeing this on Monday is very likely to unsubscribe, just from being overwhelmed.
While there may be times when you send a few messages in a short amount of time, keep in mind the volume of mail that people have to sort through each day.
If your messages are literally dominating their inboxes, they're going to unsubscribe out of self defense.
Not Frequent Enough
However, you have to make sure that you do stay in touch with your subscribers regularly enough that they don't forget who you are. This can happen with lists of any age - a lapse of several months between messages can definitely result in unsubscribes when people get a message out of the blue.
Keep tabs on your list - if it has been a few weeks since they've heard from you, try sending them something in order to keep in touch.
Note that this doesn't have to be elaborate - look for content on your site, recent blog posts, or the like.
People who get email they either do not expect or did not ask for are prone to unsubscribe. It's important to make sure that your subscribers know what to expect when they sign up for your list.
It's Not Clear They're Subscribing
Forms that offer potential subscribers free ebooks or other bonuses can increase the number of people who subscribe to your mailing list.
Unfortunately, if the offer is emphasized and the fact that the form is in fact a subscription to a newsletter is not, you may run into people who have no intention of joining your list being added. Take a look:
This form lets me know about the free stuff I'd get by signing up - but if all I want is the free stuff, I have no incentive to actually stay on your list.
Try offering value over time, through the content of the messages that you'll be sending. If they're subscribing in order to get your messages, they'll be on your list longer than if they subscribed to get a free download.
Expectations Were Not Set Correctly
In this vein, it needs to be clear to your subscribers what kind of messages they can expect to receive.
If your web form advertises a newsletter of information on your industry, but your messages contain nothing but links to your products, subscribers can easily become disillusioned and start to unsubscribe from your list.
Keep in mind that linking back to your website and your product is fine (in fact, every message you send should have a way for people to get back to your website if they so desire) - just make sure you are holding up your end of the bargain made when someone subscribed to your list.
Deliver the content that you offer on your site, and your list will be happier (and larger).
Branding is an important part of any campaign, and plays a large role in preventing unsubscribes. A well-defined, recognizable brand means that subscribers will know who the message is coming from, and remember the past value they've gotten from your messages or products.
Conversely, weak branding can result in confusion on your subscribers part over who you are or why you are sending messages to them - one step from unsubscribing.
Lack of Name Recognition
When someone first sees that they've received an email, they see the subject line and the name or email address of the sender.
If neither of these things clearly explains who the email is from, subscribers are very likely to assume that the message is spam, resulting in either an unsubscribe or spam complaint.
This message is from "events," which doesn't tell me anything, and the subject line is equally vague.
The name of the company or website should appear in AT LEAST one of those two areas - if not both!
Branding is more than subject-deep. The layout of your messages should be recognizable as well.
If a subscriber opens your message and sees something that looks completely different than what you normally send, they're more likely to not make the connection with their past relationship to you, your company, and your website, meaning they're more likely to unsubscribe.
This doesn't mean that you have to always send the same exact content, or even that you can't shake things up from time to time - just make sure that your messagess are all recognizable as coming from you.
Consider finding a template that works with your website and sticking with it can definitely help increase recognition and familiarity with your list.