Question : SMTP 553;5.1.3 error

We are having a problem sending to one company.  We are getting the following error back.

 user@customer.net on 11/29/2006 1:59 PM
            The format of the e-mail address is incorrect.  Check the address, look up the recipient in the Address Book, or contact the recipient directly to find out the correct address.
            < outgoing1.broadwing.net #5.1.3 SMTP; 553 Dynamic pool 65.90.208.26. <http://unblock.secureserver.net/?ip=65.90.208.*>>

This is not happening with other outgoing mail.

Thanks!

Answer : SMTP 553;5.1.3 error

This is a very comon thing lately. People are beginning to block e-mail from IP addresses that do not have reverse DNS configure on them to point back to your mail server name.

Yes your ISP has to do something, but will do nothing until you ask them to. You need to request that they set up an rDNS entry for the IP addresses you are using on your mail server to pint back to your mail servers name.

THEN you will have to request the specific IP address you are using be REMOVED from this block list.

I have had to do this on all of my clients servers. They are many services out there now blocking dynamic IP addresses. They consider MOST DSL addresses to be dynamic. You have to have rDNS set up to get removed from these lists.

This will only get worse as more people use these services.

It sucks...