Confusion over how header checksum values are used

Vernon Schryver
Thu May 15 15:35:09 UTC 2003

> From: Paul Wright <>

> In <>, where we're
> discussing a possible DCC plugin for Spampal, James Day says that:
> "The DCC will happily return counts for various header fields if you don't
> have a body yet. Headers alone will identify many bulk senders based on
> last received line or from address in the header."
> I know from the output of dccproc that the DCC produces these checksums,
> however, I didn't think that they were reported to the servers or used for
> filtering. Sounds like I might have misconstrued this, however. Can
> someone clarify this for me? ISTM that header checksums wouldn't be
> particularly useful for filtering as they wouldn't have enough useful
> variation in them (in the case of Received IPs) or would have too much (in
> the case of From and Subject addresses).

DCC clients report all checksums except the envelope Rcpt_To and the
second through last substitute checksums to the DCC server.  Unless
specially configured, the DCC server will have no records for any except
the body checksums and so will respond with a count of 0.  However, those
checksums can appear in either the server or client whitelists with
counts of "ok" or "many."  In other words, they can be used for blacklist.

Vernon Schryver

More information about the DCC mailing list

Contact by mail or use the form.