Re: avoiding overload on port 587
- On 11/30/2012 7:27 AM, Tomas Macek wrote:
> On Fri, 30 Nov 2012, Wietse Venema wrote:Tomas, there is a really easy solution to this problem of yours, and it
>> Strange, do you really expect Postfix to flip status immediately
>> when load drops under the limit, or do you expect it to behave in
>> a more rational manner and announce that "peace has come" when the
>> load has stayed under the limit for some minimal amount of time?
> And what is the minimal amount of time? I'm still unable to find it, how
> much time that means.
doesn't take in depth technical understanding of the inner workings of
Postfix to achieve it.
Simply physically separate your inbound public SMTP traffic from your
user submission relay traffic. I.e. setup a separate dedicated box that
ONLY performs submission on TCP 587 with auth and outbound relay. I.e.
disable the smtpd server on TCP 25. And implement Postscreen on the
current public SMTP server.
Inform your clients that the change will be complete in 14 days, or
whatever time frame you choose, and that they must switch submission to
the new IP+port with username and password before that deadline. After
the deadline, disable submission/relaying on the public SMTP server,
forcing stragglers to convert to using the new submission server.
Separating these functions doesn't require a second physical server, but
it has a number of advantages for you and your users. First is that it
fixes the problem of high public SMTP traffic causing problems for
submissions. Second, if you have to take one server down for hardware
maintenance only one function goes down, not both. Third, if desired,
you can locate the two servers in different locations, on different
networks. Etc, etc.
Many orgs with high traffic loads separate the public SMTP and user
submission functions onto separate boxes. Some have entire farms of
servers dedicated to each function.
- On Tue, Dec 04, 2012 at 07:46:10AM -0600, /dev/rob0 wrote:
> On Tue, Dec 04, 2012 at 11:59:01PM +1300, Peter wrote:Or better yet: replace it with postscreen.
> > I would still also set up port 587 on the mail.example.com
> > IP as submission as well and try to encourage your users (at
> > least the ones you can) to use port 587 from now on.
> What I would do, on Linux with IPv4 only, is create the submission
> port and use an iptables redirect for the alternate IP address:
> # iptables -vt nat -A PREROUTING -p tcp --dport smtp -d \
> mail.example.com -j REDIRECT --to-port submission
> This saves the overhead (system and administrative) of running
> another smtpd on [mail.example.com]:25; he can leave his "smtp ...
> smtpd" service alone in master.cf.
> I should also add as a reply to Stan in the other subthread: lookTo clarify, I meant that if those Outlook Expresses are not yet
> above at the first quoted paragraph: "Outlook Expresses setup with
> ... default configuration."
> Yikes, bad news, very bad. If not doing content filtering nor
> policy limitation of submission now, he will be soon. And possibly
> losing his job in any case. Tomas is not in a good place right now.
compromised by malware, they will be, soon.
http://rob0.nodns4.us/ -- system administration and consulting
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