The domain itself will not cause a penalty. However, because the .ol TLD is non-standard, receiving mail servers (especially those with strict filtering, like Gmail) may treat the email with increased suspicion. This could result in your message being flagged as spam or failing to be delivered, which can indirectly harm your sender reputation over time.
When you send an email, your mail client generates a to help servers track the conversation thread. Usually, this ID includes the sender's domain (e.g., @gmail.com or @outlook.com ). However, certain Microsoft applications use hxcore.ol as the domain suffix for these IDs. hxcore.ol
Tip: Signal tasks to stop and join them before final shutdown. The domain itself will not cause a penalty