outgoing emails being rejected

[Goldenboy]

I am trying to respond to some Craig's List posting but my email come back to
me with this message - what does it mean??

This is the mail system at host smtp0.av-mx.com.

I'm sorry to have to inform you that your message could not be delivered to
one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can delete your own
text from the attached returned message.

The mail system

<[email protected]>: host mxi1s.craigslist.org[66.150.243.1] said:
554 <smtp0.av-mx.com[137.118.16.56]>: Client host rejected:
smtp0.av-mx.com
is blacklisted (in reply to RCPT TO command)

 

[Mary]

Not your fault. The receiver's server will not accept mail from your server.
It sees it as junk and blocks it. More info here:
http://www.av-mx.com/contact/?flag=X4&ip=24.117.231.142