[imp] weird DB error

[Kevin Konowalec]

Running the latest versions of horde & imp.  I'm seeing these messages  
in my logs:

Jul  7 15:20:59 src at dabc1 HORDE[16186]: [imp] DB Error: constraint  
violation: INSERT INTO imp_sentmail (sentmail_id, sentmail_who,  
sentmail_ts, sentmail_messageid, sentmail_action, sentmail_recipient,  
sentmail_success) VALUES ('', 'webaddmin at ualberta.ca', 12144653459, '<20080707152058.111419adfnadh9kg0 at webmail.ualberta.ca 
 >', 'new', 'webaddmin at ualberta.ca', 1) [nativecode=1062 ** Duplicate  
entry '0' for key 1] [pid 16186 on line 85 of "/var/www/horde/imp/lib/ 
Sentmail/sql.php"]


It doesn't seem to be impeding the sending or reciept of mail but I'd  
still like to stop the messages.  How is the "sentmail_id" field value  
generated?  I don't know it it makes any difference (doesn't appear  
to) but I've unchecked $conf[maillog][use_maillog] in the imp "other  
settings".  Hasn't really done anything tho.

What can I do to stop this error?