According to online data, the majority of marketers remove inactive subscribers from their email lists after a period of 15 months of inactivity. Ideally, you should update your email list every 6 months by removing those subscribers who’ve always been inactive or stopped engaging. If you don’t, it can hurt email deliverability. However, before you delete them, first send a win-back email. This way you might be able to get some subscribers to start engaging with your email content again.