Hi everyone, im having problems sending emails to a specific domain: leon.gob.mx when i try to send something, it returns the following error: The e-mail system was unable to deliver the message, but did not report a specific reason. Check the address and try again. If it still fails, contact your system administrator. <sbsxopan.xopan.com #4.0.0 smtp;450 Client host rejected: cannot find your hostname, [201.151.237.146]> what could be the cause? Thanx Jorge

It looks to me like the receiving domain is performing a reverse lookup on your sending SMTP host's IP address. Because it can find no PTR record for [201.151.237.146] it rejects the connection. This is an anti-spoofing mechanism implemented by some SMTP gateways. The likely fix is to ensure your sending hosts PTR record is registered in DNS. Tony www.activedir.org

Thank you very much tony. i'll check the dns configuration.

Maybe it is not the DNS Configuration, Maybe you just never Setup the PTR with your ISP provider. This was my problem: We are getting the next error in our exchange: <mail.trueld.com #4.0.0 smtp;450 Client host rejected: cannot find your hostname,[100.99.98.97]I did a research on the error and i found the some servers request for this information "This is an anti-spoofing mechanism implemented by some SMTP gateways. The likely fix is to ensure your sending hosts PTR record is registered in DNS"I ran a DNS report: and we have the next info:97.98.99.100.in-addr.arpa Information_From_your_ISP_PTR (Your ISP Info)I read on Internet that we have to contact our ISP provider an request to create a PTR for our IP Address with the PTR Information. So, the first time some weird, but i submited a ticket with my isp and work for the next day. So, Hopefully it will work for you...... I found all tis information in many forums and i put in one for you guys. Good luck!

Thanks for the advice!!!