I am getting the following error when trying to send an email message to a local user:

A network service error has occurred.

dump - function() {
return "AjxException: msg="+this.msg+" code="+this.code+" method="+this.method+" detail="+this.detail;
msg - system failure: MessagingException
code - service.FAILURE
method - ZmCsfeCommand.invoke
detail - soap:Receiver

Any ideas as to what may be the problem?