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Re: Does Zmailer fork?

On Wed, Jun 27, 2001 at 03:23:55AM -0400, Philip Mak wrote:
> When doing remote deliveries, does Zmailer need to fork a subprocess for
> each SMTP server it has to contact?

    The "smtp server"  is for receiving messages,  the "smtp TA" is
    for sending.   In both cases for each incoming, and all outgoing
    destinations there are individual processes running.

    Implementing e.g. smtp reception in threaded manner is certainly
    possible, but very unwieldy.  Transmission is even more unwieldy.
    (Indeed the smtp-receiver has been coded in a manner where data
     related to currently active connection is attempted to localize
     into  SmtpState  structure.)

    The  smtpserver's  configuration  (smtpserver.conf)  has variable
    for limiting the number of accepted parallel connections (and thus
    the number of parallelly running processes):  MaxParallelConnections

    ZMailer can, however limit the number of transmitting processes.
    For long time the scheduler's "MaxTA" was set on 200, because
    at Solaris systems one can not use more than 255 file descriptors
    when using stdio.

> The reason I'm asking is that I have an account with an ISP that has a
> limit on the number of concurrent processes (it's an oddball "virtual
> server" configuration where I have my own set of daemons), so I'm trying
> to determine what a good MTA for this situation is.

   It all depends on what is your process-budget ?
	10 ?
	100 ?
   With the lower limit, there are definite troubles with anything.

   Possibly sendmail -- it can be configured to always place messages
   into spool at reception, and then you can have one (or two) queue
   daemons scanning the spool and pushing things out.

   It is slow, but if you absolutely can't have more than 10 or so
   processes, that is about the only setup you can have.

   For message receiving the sendmail does fork for each incoming

> I'm currently using qmail to run a discussion list with 3000 users, but
> sometimes there's a lot of slow destination SMTP servers that tie up my
> qmail processes.
> -
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/Matti Aarnio	<mea@nic.funet.fi>
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