There can be several reasons why your open rate may be dropping. Here are some common factors to consider:

1. Email deliverability issues: If your emails are not reaching recipients’ inboxes and instead landing in spam folders or being blocked by email filters, it will negatively impact your open rate. Factors that can affect deliverability include poor sender reputation, high bounce rates, irrelevant or spammy content, and technical issues with email configuration. Monitor your deliverability metrics and take the necessary steps to improve them.
   
2. Inactive subscribers: Over time, your email list may accumulate inactive subscribers who no longer engage with your emails. If a significant portion of your list consists of inactive subscribers, it can drag down your open rate. Consider implementing re-engagement campaigns to win back inactive subscribers or remove them from your list to maintain a more accurate engagement metric.
   
3. List fatigue: If you frequently send emails to your subscribers without providing sufficient value or relevance, they may become disinterested or overwhelmed, leading to lower open rates. Ensure your email content remains fresh, valuable, and tailored to your subscribers’ interests and preferences. Segment your list and personalize your emails to deliver more targeted content.
   
4. Change in subscriber behaviour: Changes in subscriber behaviour, such as different email usage patterns or preferences, can impact your open rates. For example, if more of your subscribers are using mobile devices and your emails are not optimised for mobile, it can lead to lower open rates. Stay updated on industry trends and adapt your email strategies accordingly.
   
5. Email frequency and timing: Sending emails too frequently or at inappropriate times can result in subscriber fatigue or overlooking your messages. Review your email frequency and consider experimenting with different send times to find the optimal schedule for your audience.
   
6. Quality of subject lines: Subject lines play a crucial role in enticing recipients to open your emails. If your subject lines are not compelling or fail to convey the value of your email content, it can lead to lower open rates. Test different subject lines, use personalization techniques, and focus on creating curiosity or providing clear benefits to improve open rates.
   
7. Email list quality: If your email list contains outdated or low-quality addresses, it can result in a lower open rate. Regularly clean your email list by removing inactive or invalid addresses and implement strategies to grow your list organically with engaged subscribers.

To identify the specific cause of your dropping open rate, it’s essential to analyse your email metrics, conduct A/B tests, gather feedback from subscribers, and experiment with different strategies. By continuously monitoring and optimising your email campaigns, you can improve your open rates and overall email performance.