Here is a list of things to consider if your emails are being delayed in delivery:

1. Review your IP address and other sender reputation settings.
2. Check for any firewalls in your network that are preventing the delivery of emails.
3. Check to make sure you are not relying on using IP addresses for email delivery.
4. Check the email's content for any potential spam filters.
5. Review any bounce messages you’re receiving.
6. Make sure you are using DKIM and SPF authentication.
7. Check any third-party providers that are used for sending emails.