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NDR's and Spam

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by ktimm 1 view

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Running Exchange 2k sp3. I currently have all NDR's turned off. Exchange doesn't send out any NDR's that arn't Internal. One of my users has complained to my boss that a client sent them an e-mail (with some kind of large attachment I assume) andbecause of the attachment being
larger then our system limit (which is currently 5 meg) the message was not delivered. Since Exchange doesn't send NDR's externally, the client never received a message saying that there mail didn't get delivered.Long story short, it's now become a problem. My boss says not
letting a valid e-mail sender know that there message was not delivered is unacceptable. My stand is letting spammers know that they hit a valid server (a spammer sends out e-mail to my server that then gets returned to them because of an NDR so they know that they have hit a "live" server(or am I mistaken on how that works)) is
unacceptable. Not to mention the fact that if I turn on the NDR's I have to clean out the smpt q ofthe server several times a day from Exchange trying to send e-mail back to spammers with spoofed or non-valid addresses. I'm trying to find a happy medium where valid senders can know
that there e-mail didn't get through but my server is more protected from spammers.

Does anyone have any suggestions to make everyone happy or what are your standard procedures?

7 replies

by blackdiamond

Hey,

We use GroupWise so I can only contribute our policy.

We do not inform any outside sources that there was an issue with something they sent to our system. We do inform internal users that there was an email that was not delivered or had issues. It is then up to them to inform the outside source that there was a problem and the responsiblity of the outside person to remedy the situation.

by brasslet

There is no one right answer to fit everyone. If you could configure Exchange to send NDRs only in certain situations, you could have the best of everything -- senders to legit accounts that simply go over a size limit etc. would get NDRs, sending to deleted or non-existent accounts would produce nothing. Unfortunately, Exchange 2000 doesn?t give a means to differentiate. When you disallow NDRs, you disallow ALL NDRs. Maybe you could write an event sink to do this, and maybe MS will include this functionality in the future, but for now the off-the-shelf product doesn?t do this.

Due to the above, you?re probably stuck with sending NDRs. For most, it really is unacceptable that legit e-mail is sometimes munched with no indication to the sender that there is a problem. Unless your server is severely restricted regarding disk space, there should be no need to clear the SMTP queue manually. Our hardware is nothing exotic, and at times I?ve had thousands of NDR?s with no problems.

Just my opinion, but I also think your concerns about letting the spammers know your server is alive and accepting mail are mostly a non-issue. It?s easy to check if an email domain is alive and well anyway, and most spammers buy lists of addresses. I doubt sending NDRs gives them much in the way of intelligence.

If you can afford it, look into the spam filters out there for help.

by frobo

Your Problem is not the Exchange Server, it is the Messaging Design. You have the same problem like many others with an active Mail-Server conected to the Internet. Nothing special i see.
First change the messaging Design, and it's not beginning atthe Exchange Server, it beginns at your provider.
ring up youre Provider an tell him that he sould forward the Mail for youre Domain to your Server. The Provider changes only the MX-Record for that, and push now the mail for your domain to your Server. Benefit: You have now no relying Problems, your ISP has got now the Problem. But this kind of things their allways dealing with.
Now configure your Exchange to only accept Mails for your Domain, and install an Filter or virus tool on your Server like Scanmail from Trendmicro. Now you can enable your NDRs for your CIO.

regards

Frobo

by ktimm

This issue has nothing to do with my provider or the MX record. MX has always and will always point directly to my server. Exchange has always been configured to only accept mail for my domain (why would I accept mail that wasn't?). Sorry man but your way off base.

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