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Stopping mail relaying

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5 replies

by stergios_nik

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Hello.

I have an Exchange 5.5 mail server. I noticed that a user of my domain can spoof its email address and send an mail to another user using a fake email address in the SENDER FIELD.

Does it mean that my server is a mail relay?
How can I stop this spoofing problem?
If you can supply me with some web links that describe how to prevent mail relaying in Exchange 5.5. it would be great.

Thank you in advance.

Stergios

5 replies

by mckaytech

The Service Pack level makes a great deal of difference as one of the things addressed in SP2 and newer was prevention of open relaying.

The links above are a good start. Most often I've seen this problem where someone has configured the server to allow relaying from the local subnet. In that case, any of your local users could spoof an address and it would still be relayed because it is from your local subnet. Similarly, if you configure it so only authenicated clients can relay, those clients could still spoof an address.

The real concern is whether people out on the Internet can use your server as a relay and either of the configurations above should prevent that.

regards,

paul

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