It’s quite difficult to accurately find the actual reason behind the gradual decrease of open rate in your campaign. For example, it might be due to the words you used while composing the email content, or some misconfiguration of your DNS server, or maybe these segments are less responsive compared to the previous segments, or the ISP is categorizing you in such a way that is causing less open rate etc.
You need to assume the reasons, work on them, and monitor the progress. We can guide and share resources on this.
For example,
You need to set the necessary DNS records to increase your email deliverability – This blog post might help you: How To Setup SPF DKIM And DMARC In AWS Account.
Also, you can set the Action URL on MailBluster. You can set it up from the Settings > Custom URL page.
You should follow these best practices:
1. The Ultimate Guide on How to Prevent Your Email Newsletters from Going to SPAM
2. Best Email Opening Lines to Hook Your Audience
3. Email Images: Complete Guide to Using Images in Email
4. Email Footer: Do Not Forget about the Last Impression