> but  doesn't  Imail  keep  a copy of the users in registry even when
> using  an  external db?

We've been here before (2 years ago, maybe)...no, it does not.

> if not, I can see where an external db query for recipients would be
> murderous.

It  _can_  be  totally  workable  and suffices for many installations.
Under  dictionary  attack is when it starts to crumble--since there is
no  substantive  difference  between  an  SMTPD  lookup  for an extant
recipient  and  one  for  an unknown recipient, the resource impact of
that  part  increases  as  much  as it would under a giant increase in
accepted mail.

> The  MXs must have their own local recipient db, so they do not pass
> dictionary  attack  queries  for  recipients straight through to any
> backend server.

"Must"?   Not   at  all.  LDAP  works  brilliantly  if  you  build  it
intelligently:  our  LDAP servers handle millions of queries per hour.
(We've been here before, too.)

--Sandy


------------------------------------
Sanford Whiteman, Chief Technologist
Broadleaf Systems, a division of
Cypress Integrated Systems, Inc.
e-mail: [EMAIL PROTECTED]

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