Good list hygiene is important for reputation, because mailbox providers want to ensure that:
- Their subscribers only receive email they want
- They filter out email their subscribers do not want
By following good list hygiene practices (such as removing unknown users from your list and unsubscribing complainers), you send a signal to mailbox providers that you only want to send email to the subscribers that ask for it.
This improves your sender reputation and helps your email get delivered to the inbox.