Deleting Icloud stored Photos - help - tried everything now icloud mail not receiving email and showing as "Undelivered Mail Returned to Sender"

Hi,

Please READ all points before making suggestion, I need expert help, not the basic steps (unless I have missed something)

Current acute problem: iCloud mailbox not receiving, showing "Undelivered Mail Returned to Sender"

Cause: iCloud Storage full, 100gb of items within icloud, only opted for the 5gb free storage.

Note 1: All photos were backed up (see screen shot) I downloaded via iCloud Windows 10 software program and Deleted them from that app.

Note 2: after backing up all photos and deleting them in iCloud app i unistalled Windows Icloud as I have no need for the program.

Note 3: Then I downgraded icloud storage from 100gb to the free option 5gb.,

Note 4: I also deactivated (decommissioned) all of my historic iphone devices that the photos were originally backed up from.

No problem for a month then when the payment for the 100gb icloud is normally due , a banner over my email alerted me to photos /videos not being up BUT the email is also not is not receiving email and showing as "Undelivered Mail Returned to Sender" when i test from another email.

Note 5: This exact problem happened 6 weeks ago and i decided to pay to an extra month storage and I also at the same time deleted EVERY iphone from my device register in icloud/itunes/apple settings

When i check icloud, none of the photos are deleted from icloud storage even tough i followed the exact steps of apple instructions of how to do this.

THIS IS URGENT AS THIS IS MY PRIMARY EMAIL, I NEED TO RESOLVE THIS URGENTLY. (Note: Email only consumes 2.5gb of icloud storage, so should be able to be free 5gb)

Solution Required: I need icloud to acknowledge the deletion of photos/videos so my icloud mail can function within the 5gb free icloud storage.