A client of mine is sending me emails, and is getting this error message. Your message did not reach some or all of the intended recipients. Subject: RE: test Sent: 18/05/2007 The following recipient(s) could not be reached: ‘Sub' on 20/05/2007 4:23pm You do not have permission to send to this recipient. For assistance, contact your system administrator. <exch01.maxnetwork.local #4.7.1 smtp;450 4.7.1 <exch07.maxnetwork.local>: Hello command rejected: Host not found> he receives my emails, but when he replies back to them, gets the error above. His companys tech guy, says the problem is my end. I am on Bigpond cable broadband in australia. I have a netgear router sharing the internet. Have had no problems there. Could someone tell what the error or how i could find out what is causing it, and possibily how to fix it. Thanks

Your symptom: Your mail server doesn't trust your friend's mail server, and so it won't accept anything from it. Why? Because it can't confirm the server's name. Your problem: Off the top of my head, two possibilities. (1) His ISP's mail server is misconfigured. I'd suspect this one if he can send emails to very few people outside of his ISP. (2) There's some problem with your ISP's DNS. Your direction: Make sure he can send email to everyone else. If he can't, have him bug his ISP. If he can, you should probably bug your ISP. Actually, both of you bug both of your ISPs and see if you can't get some sort of dialog going between them.