Hi!

Maintaining the database hygiene has many benefits and strongly influences the quality of the sent campaigns. Lack of base hygiene affects the deliverability of sent messages. Unused mailboxes are transformed into spam traps that are used to identify spammer accounts. Therefore, it is not worth to keep all your contacts in the database forever. It is worth running a win-back campaign among the inactive ones to see if they are real people or empty mailboxes. Accounts that do not respond in any way should be deleted.

The benefit of this practice is regaining the real state of your contact base, which can contribute to increased sales. Collecting information on how recipients respond to messages will allow you to better tailor your offers and communications to their interests and expectations.  

More information on effective database hygiene can be found in the following article:

https://blog.salesmanago.com/marketing-automation/database-hygiene-in-5-easy-steps/