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RE: pop server in an ISP environment

  • From: Roeland Meyer (E-mail)
  • Date: Mon May 29 13:21:04 2000

I have run qpopper in HA/high scale environments. Yes, efficiency
could be improved. However, it is one of the few POP3 daemons
that implement XTND XMIT functionality. The client-base at the
time was pure Eudora and we could give them POP3-only access
using qpopper, over an SSH tunnel. For this, we needed XTND XMIT
and qpopper is the only readily available POP3 daemon that
delivers it. It is, in fact, the reference standard for that

The theoretical limit, on most Unix kernels, is 64K users. This
is only because the internal representation of the uuid is
usually an int. On 64-bit kernels, it is much higher because the
definition of "int" is bigger. In reality, the max capacity of
the host is strictly dependent on the hardware architecture, how
many concurrent sessions, and what the users are actually doing
with each session.

Your 5000 user limit, based on /etc/passwd, is bogus. For
example, on Intel hardware, you will never approach even 500
concurrent shell users (developers) without the silicon melting
down. However, a Sun e10K can handle 5000 of such users easily.
That same Intel box can handle over 10000 mailboxen, if you give
it enough disk space (RAID0 spool) and memory (RAM cache) [but
not on a single 56Kbps port <g>].

> Dmitri Krioukov: Monday, May 29, 2000 8:43 AM
> qpopper was written without even slightest thought about
> performance issues. there is a lot of other pop3 daemons
> written much more efficiently. (i don't any other that
> would perform worse than qpopper). try cucipop, for
> example. it was written by the same guy who wrote
> procmail. the source code is unreadable in both cases.
> > Muljawan Hendrianto: Friday, May 26, 2000 5:38 AM
> >
> > I would like to have your opinions regarding pop server
set-up in
> > an ISP environment, what would be the common software used,
> > authentication type etc.
> >
> > I am thinking about using QPOPPER+procmail, but some people
> > that it is not scalable because its authentication is based
> > /etc/passwd. And in Unix environment there is certain
> > recommendation not to have more than 5000 users in
/etc/passwd file.