Not receive mail "Disk quota exceeded ???

[verdemamus]

Hello to all I do not speak English,
I do not succeed to receive the mail, the error that they give to me on /var/log/mail.log
and following:

May 21 22:54:10 linux imaplogin: Failed to create cache file: maildir_lock (web3_web)
May 21 22:54:10 linux imaplogin: Error: Disk quota exceeded
May 21 22:54:10 linux imaplogin: Failed to create cache file: maildir_lock (web3_web)
May 21 22:54:10 linux imaplogin: Error: Disk quota exceeded
May 21 22:54:10 linux imaplogin: LOGOUT, user=web3_web, ip=[::ffff:127.0.0.1], headers=0, body=0, time=0

I have tried in any case but I do not succeed.
Thanks
By
Simone