USPS Informed Delivery E-mail Not Being Delivered Anymore to my Xfinity Account Inbox

I was regularly receiving the USPS Informed Delivery E-mail showing mail and packages I will be receiving that day.  A several days ago, I inadvertently moved the e-mail to my Spam folder and than back out again (not Spam).  Since then I have not received any Informed Delivery E-mails even though I have marked the sender's address as not spam.  Informed Delivery says they are still sending the e-mails. After looking through the forum, I noticed several others are having the same problem. It appears the emails are being facilitated by Mailgun and my e-mail address is on some type of suppression list, which Mailgun manages.  Need help in getting my info off the suppression list and my Informed Delivery e-mails again delivered to my Xfinity inbox.  Thank you in advance for helping resolve this issue.