A customer was suddenly unable to have emails sent from their shopping cart using smtp authentication via cdosys. Changing to an alternative port fixed the problem. Tech supports answer when I pointed this out was that the standard smtp port is checking blacklists. Further investigation found the web server ip on a blacklist and caused the problem. So it appears to me that Jodos webserver is being blocked by Jodos mailserver due to the fact that there is no rDNS for the web server IP as stated in the blacklist report given by spam cannibal.