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       postal - program to test SMTP mail server throughput.


       postal [-m maximum-message-size] [-M minimum-message-size] [-t threads]
       [-c    messages-per-connection]    [-r     messages-per-minute]     [-s
       ssl-percentage]  [-l  local-address]  [-a]  [-b  [no]netscape]  [-[z|Z]
       debug-file] [-f sender-file] smtp-server user-list-filename


       This manual page documents briefly the postal, program.

       It is designed to test the performance of SMTP email servers by sending
       random messages to the specified server as fast as possible.

       The  smtp-server parameter specifies the IP address or name of the mail
       server that the mail is to be sent to.  Mail sent by  Postal  will  not
       use  MX  records, this is to allow testing outbound relays etc.  If you
       want to specify a port other than port 25 then enclose the host address
       in square brackets and have the port address immidiately following.  If
       you want a DNS lookup for every  connection  (for  testing  round-robin
       DNS)  then  immediately  preceed the host address with a ’+’ character.
       To specify multiple servers  for  round-robin  use  then  seperate  the
       addresses  with  commas.  Note that localhost is used for connecting to
       the same machine.

       The user-list-filename is the name of a file which contains a  list  of
       user’s email addresses.  This can be just user-names or fully qualified
       email addresses.  Whatever you specify will be sent exactly in the SMTP
       protocol  so  make sure you do whatever is appropriate.  If unsure then
       use fully qualified addresses (IE

       The sender-file contains a list of users that  will  be  in  the  From:
       field and envelope sender of the messages.  If it is not specified then
       the user-list-filename will be used for the sender list.

       The maximum-message-size indicates the size in Kilobytes that  will  be
       the  maximum  size  of the message body.  The size of each message body
       will be a random number between 0 and the maximum size.  Specify "0" if
       you  want  just headers to test the connection rate.  The default value
       is 10.

       The threads parameter is the number of threads that should  be  created
       to  attempt  seperate connections.  A well configured mail server won’t
       accept an unlimited number  of  connections  so  make  sure  you  don’t
       specify  a number larger than the number your mail server is configured
       to handle.  Also for sensible results make  sure  that  you  don’t  use
       enough   to   make   your   server  thrash  as  the  results  won’t  be
       representative of real-world use.  The default value is 1, this default
       is   not   suitable   for  real  tests,  it’s  just  for  testing  your
       configuration.   If  you  specify   multiple   server   addresses   for
       round-robin use then this number of threads will be created per server,
       IE 4 servers and -p5 will give 20 threads total.

       The messages-per-connection parameter is  for  sending  more  than  one
       message  per SMTP connection.  The default value is "1".  A value of -1
       means to send an indefinate number of messages on  one  connection  (~4
       billion).   If  a  value  > 1 is specified then the number sent on each
       connection is a random number between 1 and the number specified.   For
       simulating a mail server connected directly to the net use a value of 2
       or 3.  For simulating a mail server connected to a front-end relay  use
       a large number.  For testing for bugs in your mail server use the value
       0 and leave it running  for  a  week.   ;)   A  value  of  0  means  to
       disconnect   without   sending   any  messages.   Good  for  testing  a

       The max-messages-per-minute parameter is for limiting the throughput of
       the  program.   This  is  designed to be used when you want to test the
       performance of other programs when  the  system  is  under  load.   The
       default is effectively 24000 messages per minute.

       The  local-address  parameter  specifies which local IP address(es) are
       used to make the outbound connections.  Specified in the  same  way  as
       the  remote  address.  This is good for testing LocalDirectors or other
       devices that perform differently depending on which source  IP  address
       was used.

       The -a command turns on all logging.  All message data received will be
       logged.  This will make it slow and it may not be able  to  saturate  a
       fast Ethernet link...

       The  -b  switch  allows you to specify breakage strings.  Currently the
       only option is for Netscape mail server which strips  spaces  from  the
       start  of  subject lines.  -b netscape means to avoid leading spaces on
       subject fields to not break Netscape.  -b nonetscape  means  to  always
       put  extra  space to test for the bug in Netscape and similar products.
       Some people say that the RFCs are open to interpretation on this issue,
       I  am  interested to see whether anyone else interprets it the way that
       Netscape does.

       The -s switch specifies the percentage of connections which are to  use
       TLS AKA SSL.  Use 0 for no SSL, or 100 for always SSL, or any number in
       between.  Default is 0.

       The -z switch allows you to specify a debugging file base.   From  this
       base  one  file  is  created for each thread (with a ’:’ and the thread
       number appended), each file is used to log all  IO  performed  by  that
       thread for debugging purposes.

       The  -Z  switch  is  the  same  but  creates  a  separate file for each
       connection as well with an attitional  ’:’  appended  followed  by  the
       connection number.


       When testing mail servers please use domains defined in http://www.rfc- -,, and
       are  all  good  options.   Please don’t use anything related to a valid
       name, that will cause pain for you and others on the net.


       0      No Error

       1      Bad Parameters

       2      System Error, lack of memory or some other resource


       This program, it’s manual page, and the Debian package were written  by
       Russell Coker <>.


       The source is available from .

       See     for     further