Inbox Placement Rate (IPR) is the percentage of sent emails that were able to reach the targeted inboxes rather than the spam or junk folders of subscribers.
If you have a low inbox placement rate, it may be due to;
Bad IP and/or domain reputation,
Constantly sending messages to invalid or unknown email adresses.
Inbox Placement Rate: Number of emails delivered to inboxes of recipients / Number of emails sent by your organization.
Remove subscribers from your list that have not engaged with your email marketing efforts in the last 90 days,
Make sure that your email service provider sends your emails at the appropriate speed,
Authenticate your email account,
Always check your emails to see if there is any issues or spam problems,
If your email deliverability score is low, do not send any emails before resolving this issue,
Send relevant campaigns to segmented customers.