One more error; sieve-spam.svbin

See lines like this constantly in my mail log.

May 06 13:48:24 lmtp(email@domain.net)<158538>: Error: open(/etc/dovecot/sieve-spam.svbin.mail.ppgcloud.com.158538.95b83c4993ba03e1) failed: Read-only file system

May 06 13:48:24 lmtp(email@domain.net)<158538>: Error: sieve: binary /etc/dovecot/sieve-spam.svbin: save: failed to create temporary file: open(/etc/dovecot/sieve-spam.svbin.) failed: Read-only file system

May 06 13:48:24 lmtp(email@domain.net)<158538>: Info: sieve: msgid=f42094d0d2610fa27ec2610a001ff329@customersclientdomain.com: stored mail into mailbox ‘INBOX’

Is there a permissions issue I should fix?

Keith.