mail refused.......source not recognizable

[Glendon]

Whenever I send mail from one of the unix systems to the outsite.&nbsp;&nbsp;It gets rejected from most sites that check for a valid source of the sender.&nbsp;&nbsp;eg. mail goes out as <A HREF="mailto:user@system.avon.com">user@system.avon.com</A> and gets rejected.&nbsp;&nbsp;What should I change in the sendmail.cf to make this work, and how will it work for mails that is replied to.&nbsp;&nbsp;Help.&nbsp;&nbsp;&nbsp;Glen<br><br>PS: We use Lotus Notes running on NT.<br>

 

[AndyBo]

This sort of problem is usually related to DNS.&nbsp;&nbsp;Make sure that your ISP, or whoever controls the DNS record for system.avon.com, has set up a reverse DNS entry for you.<br><br>If memory serves correctly, what the remote mail servers will be doing is extracting the domain name from the sender address.&nbsp;&nbsp;It then takes the IP address of your mail server that it will have from the SMTP connection.&nbsp;&nbsp;It does a lookup of the domain name that is related to the IP address (a reverse DNS lookup).&nbsp;&nbsp;If the domain name it gets does not match the domain name in the sender address, your email gets rejected.<br><br>Now, if you have not got a reverse DNS entry set up, when the remote mailer does it's reverse lookup on, for example, 194.123.11.22, it does not get a domain name sent back.<br><br>Why do the remote systems do this?&nbsp;&nbsp;Mainly, it's for protection against being used as a spam relay.&nbsp;&nbsp;It is also a validation that the e-mail is being sent from the correct place.&nbsp;&nbsp;It is <i>extremely</i> trivial to forge the senders address, and the From: address, in an outgoing e-mail, and most spammers do this.&nbsp;&nbsp;(Ever received an e-mail from 12345@67890.12345?...)&nbsp;&nbsp;If the mail server can take the mail message and confirm that the sender's domain is hosted on the mail server that is sending the mail, then the sender is probably valid.<br><br>Why might you not have a reverse DNS lookup?&nbsp;&nbsp;Well, if you control your own DNS, you probably didn't know you needed it.&nbsp;&nbsp;If your ISP controls it, then it's cost and effort saving on their behalf.&nbsp;&nbsp;To set up the reverse DNS for a domain name means that they have two records to control.&nbsp;&nbsp;Speaking from experience, if you are setting up a DNS record, it takes about 30 seconds to a minute longer to also add in the reverse DNS entry for the domain...<br><br>Anyway, I hope I've not wandered too far off track, and I hope that solves your problem. <p> <br><a href=mailto: > </a><br><a href= > </a><br>--<br>
0 1 - Just my two bits