Webmail Storage

What is this?
Webmail Storage

There is no limitiaon on disk space , why I got this error?

Which hosting provider is this? And is this a mail screenshot?

I found this email in my server that runs cyberpanel.
I dont know where is come form.
But in header , the sender was cybepanel.net

Quite strange. I haven’t come across any such mail though.

What was the full email address you received this mail?