postini rejected mail, but why?

phrea84 used Ask the Experts™

We are running SBS 2011.  It's been in production for 2 months and things are good.  Today we discovered we can't send to a particular domain.  I was able to determine they are using postini for spam-filtering, but can't figure out why we are blocked.  What's more, the bounce back makes no sense--it shows OUR email address as intended reciepient.  See below

Postini rejected your message to the following e-mail addresses:

Postini gave this error:
Verification failed for <> The mail server could not deliver mail to The account or domain may not exist, they may be blacklisted, or missing the proper dns entries. Sender verify failed

A problem occurred during the delivery of this message to this e-mail address. Try sending this message again. If the problem continues, please contact your helpdesk.

Diagnostic information for administrators:
Generating server: exchange.domain.local
Postini #550-Verification failed for <> 550-The mail server could not deliver mail to The account or domain may not exist, they may be blacklisted, or missing the proper dns entries. 550 Sender verify failed ##

2 questions--why is this happening and how do I fix?  I tried routing through our ISP and it bounces as well.  a check on our domain at comes back good on both smtp and RBL

Please help.
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Properly using Postini can be a tricky affair, and Google does seem to change the rules somewhat regularly (I no longer support clients on Postini for this reason.)  In short, this is not an error on your end, as your NDR clearly indicates. Postini, or the domain owner's configuration of how Postini filters, is not working properly and you can't change that for them.  You can try to contact the domain owner and inform them of the issue, but there is little else you can do.

on your email server, go to and write down your external IP address.

then verify that your reverse dns record for your email server's external IP address match the name that your server is providing to the world.

for example:  my exchange server says its name is

so my reverse dns record for my email server's public IP address must read

if you did not MANUALLY setup a reverse DNS record for your email server's public IP address, that is most likely the cause ("missing proper dns entries").


reverse dns is setup and resolves properly.  

so am i stuck basically telling the reciepient they need to fix it?  nothing i can do on my end?
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