iCloud Email Inbox Full

Since January, I have not been able to receive or send any emails from my iCloud account; this has been happening since I canceled the iCloud+ plan (it is now at 5GB and says full, but I do not understand why because I cleared up my space). I have cleared my entire photo gallery and freed up 23 GB of space. However, I have noticed that I still could not receive or send any emails. How would I fix this?