As of the last couple of days, one of my users gets a message from our server every time he sends an email to an address email@example.com. The message says that this is a warning only and that the email was going to be sent on a delay. Another user was unable to send an email to craigslist with the attached message. subdomain.domain.local is our email server and 126.96.36.199 is our public static IP address. Both issues seem to be related to MX records. I'm not sure the best way to approach this. I understand what DNS is and what it does, but I'm unsure as to whether I need to setup a Reverse lookup on my server, if I need our ISP to create a PTR for us, or what I need to do in order to get both of these working. Any help is much appreciated.
The following recipient(s) could not be reached:
firstname.lastname@example.org on 5/1/2009 11:15 AM
You do not have permission to send to this recipient. For assistance, contact your system administrator.
<subdomain.domain.local #5.7.1 smtp;554 5.7.1 <adsl-1-1-1-1.dsl.lsan03.pacbell.net[188.8.131.52]>: Client host rejected: Please_use_SMTP_relay_of_your_isp,_or_setup_non-generic_dns.See:_http://www.craigslist.org/about/help/generic_DNS xabd-276>