Check if valid user before scanning

[John Hinton]

My mailserver is getting pounded with mail sent to invalid usernames at our
hosted domains. Today, there have been about 1200 viruses sent so far, of
which only about 20% were to real mail accounts. Is there a way to allow the
checking of a valid username before scanning begins? If the account doesn't
exist bounce or dump it, but for sure not use the resources.

I'm using RHEL 3.0 and sendmail and have procmail running as well. Using
ClamAV as the AV package running as a deamon. This thing takes a bit of
horsepower! Looking for ways to stop the waste of processor power on the trash.

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