554 5.7.1 <yourhost.yourdomain.com[10.10.10.1]>: Client host rejected: please_use_SMTP_relay_of_your_isp,_or_setup_non-generic_dns.
In an effort to curb abuse of our email servers and limit the amount of spam inflicted upon our users, craigslist does not accept email from computers with dynamically assigned IP addresses, or hosts that have generic DNS setup.
The easiest solution is to use the mail server of your ISP to relay your email, as they almost certainly have their DNS setup properly in the way we would like. If you're not sure how to setup your mail client to do this, please contact your ISP.
If you have a static IP address and want to be able to send email through your own mail server, you will need to contact your ISP and have them setup non-generic DNS for your IP address. Usually this is done via a PTR record. Note that you'll need a matching A record. Again, the easiest solution for most end users is to route their outbound email through the mail server of their ISP.
If these suggestions don't work, some people find it easiest to use one of the many free web based email systems.
When you make a connection to our servers, we use your IP address to perform a reverse lookup to find the name listed for your computer in the domain name service. We consider you to have generic DNS if the hostname returned contains:
If you have a static IP address, run a mail server and do not have generic DNS, and are continuing to run into trouble, please send email to firstname.lastname@example.org. Be sure to include the complete headers and rejection message, so that we're able to determine exactly what is happening.