Getting around ISP SMTP firewall settings (Re: Submitting a new port if send-pr is broken)

Giorgos Keramidas keramida at
Mon Nov 26 03:16:48 PST 2007

On 2007-11-26 04:00, "Aryeh M. Friedman" <aryeh.friedman at> wrote:
>BTW I a redirected this to -questions
>> You should be able to set up a local mailer/MTA (sendmail, postfix,
>> etc.) and tell it to use your ISP's mail server on TCP port 25, and
>> it all should just "magically work" unless they require SMTP AUTH
>> (not many do from what I've seen; they base authentication on the
>> source IP of customers).
>> sendmail refers to this feature as SMART_HOST, while postfix refers
>> to it as a transport destination (see transport(5)).
> I have not set the MTA up yet for it but I did test it with
> thunderbird... an other question how can I set it up that I can
> receive mail (dynamic IP and 25 inbound is blocked)?

Thunderbird doesn't necessarily go through an SMTP connection to the
local host, so it may work with or without a local MTA installation &
setup (depending on which host you forward outgoing email).

If you set up Thunderbird to use `localhost' for outgoing email, then
you have to also configure a local MTA (Sendmail, Postfix, or qmail are
popular choices).

I don't think there's an easy way to set up the local Sendmail
installation to *receive* email from the world without some sort of
`static address' though.  To do that, you would have to work with your
ISP, so that:

    * Your address does not change semi-randomly or ramdonly.

    * Your fully qualified domain resolves correctly and its MX records
      point to your static IP address.

    * Your incoming port 25 traffic is not filtered.

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