Many 550 5.7.1 NDRs -Why?

[GellyBelly]

Hi,

Some of our users are getting 550.5.7.1 NDR as follows:

You do not have permission to send to this recipient. For assistance, contact your system administrator.

<exchmail.KINEFAC.LOCAL #5.7.1 smtp;550 5.7.1 <evandy@destindomain.net>... Relaying denied>

I have done some research and suspect the destination servers have "Sender ID" activated and that my server is not sending out SPF DNS record when the destinatiion server
is requesting one. Does anyone know if I am on the right track here?? If so, how do I activate our SPF record??

The users here are getting a little frustrated that there emails are being rejected where they were not before. A good % of the destination addresses are foreign, if that helps.

Here is a link to some info on the SPF:

http://www.msexchange.org/tutorials/Sender-Policy-Framework.html

Thanks

Gerry