[horde] Horde suddenly stopped sending email

[Olu A]

My Horde (Installed with plesk) was working just fine until it just stops delivering emails.  I also have Atmail client on the same server, emails sent through Atmail are delivered just fine.
below is the maillog entry when sending emails through horde;

Aug  2 10:52:12 websvr qmail-queue-handlers[17800]: Handlers Filter before-queue for qmail started ...
Aug  2 10:52:12 websvr qmail-queue-handlers[17800]: from=-- at hostname.domain.com
Aug  2 10:52:12 websvr qmail-queue-handlers[17800]: hook_dir = '/usr/local/psa/handlers/before-queue'
Aug  2 10:52:12 websvr qmail-queue-handlers[17800]: found handlers entry = '/usr/local/psa/handlers/before-queue/global/10-spf-uXVbMv'
Aug  2 10:52:12 websvr qmail-queue-handlers[17800]: call_handlers: call executable = '/usr/local/psa/handlers/info/10-spf-uXVbMv/executable'
Aug  2 10:52:13 websvr spf filter[17801]: Starting spf filter...
Aug  2 10:52:13 websvr spf filter[17801]: Some args not defined. Use /usr/local/psa/handlers/info/10-spf-uXVbMv/executable <FROM> <TO>
Aug  2 10:52:13 websvr qmail-queue-handlers[17800]: call_handlers: Error during call '/usr/local/psa/handlers/info/10-spf-uXVbMv/executable' handler
Aug  2 10:52:13 websvr qmail-queue-handlers[17800]: LOG Internal error in handler '10-spf-uXVbMv'. Skip handler.
Aug  2 10:52:13 websvr qmail-queue-handlers[17800]: starter: submitter[17802] exited normally
Aug  2 10:52:13 websvr qmail: 1249235533.035126 new msg 14518153
Aug  2 10:52:13 websvr qmail: 1249235533.036794 info msg 14518153: bytes 626 from <-- at hostname.domain.com> qp 17802 uid 48
Aug  2 10:52:13 websvr qmail: 1249235533.050984 end msg 14518153
Aug  2 10:52:13 websvr imapd: 1249235533.142373 LOGOUT, user=email at domain.com, ip=[127.0.0.1], headers=0, body=0, rcvd=628, sent=561, maildir=/var/qmail/mailnames/domain.com/info/Maildir


The log indicates missing <From><To> args but i dont know where i can fix it in Horde, I have searched everywhere for help without luck and i am hoping someone here can give me an advise on where to look to resolve this. 

thank you