/var/mail/root for user root. error writing message: File too large

Hello to everyone.
How to resolve this issue?


This is the mail system at host xyz.dominio.local.
I’m sorry to have to inform you that your message could not be delivered to one or more recipients. It’s attached below.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can delete your own text from the attached returned message.
The mail system
<root@xyz.dominio.local> (expanded from ): cannot update mailbox
/var/mail/root for user root. error writing message: File too large

Thanks to all.
Luca.