When I try to send a message to any email address, I get the following error Report:

msg - Message not sent to any recipients because of these failed addresses: sardiskan@gmail.com
code - mail.SEND_FAILURE
method - ZmCsfeCommand.invoke
detail - soap:Sender
constructor - 
function ZmCsfeException(msg, code, method, detail) {
    if (arguments.length == 0) {
    AjxException.call(this, msg, code, method, detail);

toString - 
function () {
    return "ZmCsfeException";

dump - 
function () {
    return "AjxException: msg=" + this.msg + " code=" + this.code + " method=" + this.method + " detail=" + this.detail;
I also got an error trying to put something in my calendar, but it didn't give me a report. Plus, it isn't giving me an error anymore. I'm running this server off of an old K6 366mhz computer for testing purposes.

I've already gone into the MTA tab and turned off DNS lookus and disabled all that other stuff in there.

Any ideas?