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qmail-verify(8)


NAME

   qmail-verify - Address verification daemon

SYNOPSIS

   qmail-verify

DESCRIPTION

   qmail-verify  receives UDP packets containing local email addresses and
   returns a single byte to indicate if the address is valid or invalid to
   the  sender  of the UDP packet.  qmail-smtpd or qmail-qmtpd are typical
   clients using the qmail-verify service, although at present only qmail-
   smtpd  has had this functionality added.  qmail-verify is based on Paul
   Jarc's realrcptto patch for qmail (http://code.dogmap.org/qmail/).

   qmail-verify uses  the  files  control/locals,  control/virtualdomains,
   users/cdb, the system password file entries (typically in /etc/passwd )
   as well as  the  existence  or  not  of  users'  home  directories  and
   .qmail[-xxx] files to determine if a given address is valid.

   Where a qmail system uses .qmail-default files on a per-domain basis in
   a virtual domains setup, this is likely  to  result  in  all  addresses
   being  considered  'valid'. This may not in fact be the case in certain
   situations, such as with extensions/adaptations to qmail like  vpopmail
   which  use  .qmail-default  files  throughout (delivery in this case is
   subsequently handled  by  a  vpopmail  component).  In  these  cases  a
   replacement  for  qmail-verify  will  be  required  that  can determine
   address validity.

   Other customised qmail installations  that  use  different  methods  to
   locate users' mailboxes are likely to need alternatives to qmail-verify
   or a modified version of it for address verification.

INVOCATION

   qmail-verify  should  be  invoked  as  user  root  to  have  sufficient
   privileges  to  determine  the  validity of a given address. In certain
   single-UID virtual domains setups, it may be sufficient to  run  qmail-
   verify as the single-UID.

   By  default,  qmail-verify  listens  on  localhost  (127.0.0.1) on port
   11113. This  behaviour  can  be  changed  by  setting  the  environment
   variable  LISTEN to specify the IP address and/or port: Set this to the
   desired IP address, optionally followed by a colon and port,  thus  for
   example LISTEN="192.168.1.1:10101".

ADDRESS VERIFICATION DETAILS

   qmail-verify  is implemented by taking the various pieces of qmail that
   parse an address and combining them  in  the  same  executable,  qmail-
   verify.  Thus logic is taken from qmail-send, qmail-lspawn, qmail-getpw
   and qmail-local.

UDP PACKET DETAILS

   The incoming packet contains just the email address to be checked as  a
   string. The string is optionally terminated with a 0 byte.

   The  response  packet  contains  a  single byte to indicate whether the
   address is valid. The lowest-order  bit  of  this  byte  indicates  the
   result:  0  for  'valid',  1 for 'invalid'. Other bits of this response
   byte are set by qmail-verify to  give  further  debugging  information;
   these other bits should generally be disregarded.

   Although  not  especially  designed  as  a  new protocol, extensions to
   qmail-verify could require the query  string  to  be  0  terminated  to
   separate  it  from  other data to follow. Currently the response packet
   contains the response byte and the 'Controlling user'; more information
   could potentially be returned if required.

CONTROL FILES

   At  startup  qmail-verify  reads  the  following  qmail  control files:
   control/envnoathost,        control/locals,        control/percenthack,
   control/virtualdomains.   If  changes  are  made to any of these files,
   qmail-verify should be restarted for the  changes  to  take  effect  in
   qmail-verify.

   If  you  are  using different machines for qmail-verify and qmail-smtpd
   you should ensure that the machine providing the  qmail-verify  service
   has  a  full set of control files as well as the mailboxes; the machine
   running qmail-smtpd still needs control/rcpthosts to be setup.

LOGGING

   qmail-verify logs  each  decision  it  makes  to  stderr:  The  address
   followed by whether it's valid or not.

AUTHOR

   Andrew  Richards,  building on the work of Paul Jarc and Dan Bernstein,
   and with plenty of help along the way from Russell Nelson, John  Levine
   and Charles Cazabon amongst others.

SEE ALSO

   qmail-smtpd(8).



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