Email has always been a great mechanism for communicating to a large group of your customers, but if you’re only using it to broadcast the same, indiscriminate message to everyone, you’re limiting its relevancy and power to drive performance.

These days, marketers celebrate their ability to use data to supercharge email – the most ubiquitous and deterministic identifier in their toolbox. This data is often a mix culled from their own CRM databases and from third parties, which can offer such insights as a person’s browsing behavior and location.

But there are mistakes marketers should avoid when integrating data into email marketing for personalization. Here are four of the most common:

1. Not having permission to send emails

You should only send emails to those who have given you the right to market to them. If you haven’t been granted that right, people can easily get annoyed seeing your messages in their inbox, and they might choose to do business elsewhere.

Those recipients may also leave your emails unopened, which could lead Yahoo, Gmail, and other email services to view you as a bad actor who should be blocked. One more repercussion: You could be fined for violating the CAN-SPAM Act, which sets the rules for commercial email.

So make sure to secure user consent before sending emails lest you lose trust with your consumers and potentially incur stiff financial penalties by the FTC.

2. Not being able to identify your customers

The browsing habits of users often create complexity for companies. Your customers often log in to a site on their desktop but later visit the same site on their mobile device, or they clear their cookies and, as a result, their identity is unknown to you.

Many companies find they can’t recognize the majority of visitors on their websites, and the problem could worsen as technology providers bend toward calls for more user privacy.

Yet, you can use identity resolution solutions to help you translate unknown customers into known ones. Having a higher percentage of known traffic is a good thing. It means you can deliver personalized messaging in the inbox more frequently and on a more timely basis (see #3 below), which will improve the performance of your email-marketing efforts.

But, please make sure you and your partners manage consumer permissioning appropriately before engaging identity solutions.

3. Not leveraging your data effectively

When you have permission to communicate through email with customers, you should use the information you have about them to improve the user experience and drive conversions.

If you know a customer has recently left a bathing suit in his/her cart, for example, you could employ dynamic product marketing to send an email with a coupon for that exact item. People have the highest propensity to click and react to the most recent product they looked at, which is why this type of retargeting works so well.

If the customer didn’t abandon his/her cart and actually bought the swimsuit, you could help that person take additional steps in his/her journey by sending recommendations for related items like flip flops or sunglasses.

Meanwhile, you could also use your data to suppress ads that would cause a bad experience. Sending loyal customers a coupon that is limited to new visitors would hit like a thud, for instance, as would sending an email about a sofa sale to a customer who recently bought a sofa.

4. Not using trustworthy and accurate data

Utilize your own data. First party data is likely the most trustworthy, accurate data available to you. Muddying the waters with unverifiable data from third party sources can get tricky. If you value your brand and engage consumers in a transparent, permission-based manner, then use your data to deliver relevant, personalized messaging. The alternative is wasted marketing spend.

In the end, one way to ensure you’re not making harmful email marketing mistakes is to work with a trusted company that is sensitive to user permissioning and demands it from their own partners; assists with identity resolution through solutions like a robust identity graph; powers dynamic product marketing in email; and offers an exchange of activation partners to magnify your effective reach.