Using version 5.0.5 community edition I was able to send emails fine until I setup the Zimbra/Funambol connector (which works great btw) but now whenever I try to send an email using the ZWC I get the error

A network service error has occurred. msg: system failure: MessagingException
code: service.FAILURE
method: SendMsgRequest
detail: soap:Receiver
trace: btpool0-0:1209155121019:cff4d05f42dcc483

Anyone know what the cause might be?