smtp authentication

[a_40]

HI,
I want to know whether simple smtp messages can send email from a remote host that only has an ip assigned by the network,(no domain) but do not have any login or password authentication.
Is it able to send email to users within a domain. I have tried to send emails using my code on computers that have domains and they have been able to send out a mail successfully.

However,I am not able to send a mail from my remote host that has a ip but no domain. The smtp message fails at the "data" section. I am able to get a response once I have sent "data" over to the server. It is only when I am constructing the message and ending it with '.' on a single line that I am unable to get a response not even an error,why?

Can anyone help, I have been trying to find an answer for two weeks but in vain.

Thanks and Regards,
Xu Weijie

[Christopher Caldwell]

If you're getting a DNS/relay type failure (due to anti-spam provisions in sendmail), you'll see a 500 series error like
500 Relaying denied


So, I'll take a bit more information to help troubleshoot your problem.

SMTP auth isn't "widely used" on the global Internet.

It's generall considered an Intern "Best Practice" to have all hosts that are directly connected to the Internet provisioned with forward and reverse names available in public DNS.

This practice prevents many SMTP mail transmission problems. In addition, the practice adds a small layer of security to your system. Finally, correct DNS provisioning helps with troubleshooting.

[Christopher Caldwell]

BTW, the answer to your question is yes, you can send to a host with only an IP. Depending on which version of sendmail you're running, you'll have to look at disabling the ruleset that says "reject mail if the from domain won't look up in DNS", and you'll probably need to add the IP for the DNSless server to your access database or equivalent.