Reduce bounce rate
Obviously, the most important thing when sending emails is to make sure the emails don't bounce. A high bounce rate will get your organization flagged in various spam blacklists. When that happens, emails that normally will be delivered to your recipients will be blocked, rendering your email marketing campaign pointless.
Maintain reputation & relationships
People come and go in any organization. When you maintain an up-to-date email list, you can be sure you are reaching the right person in charge. This ensures you are able to communicate effectively to build brand awareness for your products and services.
Increase conversion rate
When you clear out inactive or invalid emails from your email list, you can put more energy and focus into converting valid prospects into paying customers. Instead of spamming thousands of emails which may bounce back, you just concentrate on marketing your products and services to those who matter.
Lessen cost of sending emails
Sending emails costs time and money. With a cleaned email list, you only deal with a smaller list but with a higher chance to reach your targeted audience.