Possible reasons for the delays...
- Email server issues
- Spam filters
- IP or domain reputation
- Network congestion
- Email size
The simple testing process for email service providers (ESPs):
- Check delivery reports: Most ESPs provide delivery reports that can show if your emails have been delayed or blocked.
- Try resending the email: If your ESP allows, try resending the email to see if the delay is resolved.
- Review email content: Ensure your email content is not triggering spam filters by avoiding certain keywords or phrases and limiting attachments. Please see the link below for the content testing.
- Check your sending reputation: ESPs often have reputation scores that indicate the quality of your email-sending practices. Check your score and make improvements if necessary.
- Test with smaller email lists: If your email list is large, try testing with a smaller group of subscribers to see if the delay is related to the size of your list.
If these steps don't resolve the issue, reach out to your ESP's customer support for further assistance.
Related article:
How to test whether your content is causing deliverability issues?