Top 4 reasons to clean your email list:
Save wasted money – a clean email list saves you the trouble of spending money to send messages to inactive and/or non-responsive addresses
Reduce spam complaints – sending to bad email addresses triggers often results in spam complaints and ISP blocks. The cleaner your list, the better your chance for delivery and inbox placement. 
Improve campaign results – higher inbox placement rates mean higher open rates. This leads to increased conversions and sales, which equals higher ROI on your email campaigns.
Reduce reputation risks – repeatedly sending to invalid email addresses can hurt the sender reputation for your company and registered domain. The higher your engagement rate, the better your delivery rate.

Email list Cleaning