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List:       postfix-users
Subject:    Re: Postfix on a small home network (without a domain name)
From:       Jef Driesen <jefdriesen () hotmail ! com>
Date:       2012-02-29 17:04:20
Message-ID: jillqk$g62$1 () dough ! gmane ! org
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On 02/29/2012 04:38 AM, Viktor Dukhovni wrote:
> On Tue, Feb 28, 2012 at 04:33:45PM +0100, Jef Driesen wrote:
>
>> With some help from a dyndns account, I can even access my imap
>> server from outside my network. This works great, except that I
>> can't send mails from outside my network. Therefore, I would like
>> to setup an smtp server that simply forwards all mail to my ISP.
>
> Indeed a submission server as you confirmed in a later message.

I should have mentioned that in my original post.

>> The first and main obstacle I encounter is the fact that I don't
>> have a real domain name. I know I can configure some fantasy name:
>
> You don't need a "domain name", specifically you don't need a domain
> with MX records, ... You clearly need a DNS entry for your server,
> which you in any case already have for IMAP so you're done.
>
>> myhostname = barracuda.home.lan
>> mydomain = home.lan
>> myorigin = $mydomain
>> mynetworks = 127.0.0.0/8 192.168.0.0/24
>> mydestination = $myhostname localhost.$mydomain localhost $mydomain
>> relayhost = [smtp.isp.tld]
>
> Fine. Your users should never see any addresses in in the "home.lan"
> domain, they will continue to configure their mail clients to use
> only the public external addresses even for mail sent locally between
> them. All you need is a virtual_alias_maps (virtual(5)) table that
> maps these addresses (envelope recipient only) to the corresponding
> local mailboxes. No smtp_generic_maps, ... required.
>
> 	virtual:
> 		user@isp.example.net	user@localhost
> 		...
>
> This way mail from your users needs no rewriting, but mail to your
> users is delivered locally (if delivery is via local(8), otherwise
> change the address class of the rewrite domain to virtual mailbox
> if that's better).

Thus the only purpose of this virtual table is to make sure that mail for local 
users is delivered straight to the local mailbox, without having to go through 
the relayhost and the isp mailbox. So it's basically taking a shortcut, right? 
Even without this table everything should work fine.

>> But I wonder if it's possible to setup postfix without a domain
>> name at all. For all other purposes (ssh, etc), I'm just using the
>> non-fqdn hostnames (e.g. user@machine), and that works perfectly.
>
> You must specify "mydomain" and more importantly "myorigin", but
> this need not belong to any of the address classes that imply any
> special handling.
>
> You need only worry about "myorigin" to the extent that you mail
> submitted locally via sendmail(1) to (often from cron(8)) to be
> delivered somewhere, this too can be accomplished with suitable
> lookup keys (bare users if you wish) in virtual(5), provided
> such mail is never sent out.

With my settings listed above, or even by just setting "myorigin=localhost", 
such mail should already be handled fine, isn't it?

> You can use canonical_maps to fix sender addresses in any mail that
> is sent via sendmail and is destined outside your domain, so for
> such users you'll have:
>
> canonical:
> 	bare-user	external-address@isp.example.net
>
> virtual:
> 	external-address@isp.example.net	bare-user

Is it possible to just refuse to relay outgoing mail with a bogus sender 
address, rather than trying to map it to a valid address?

The reason why I'm asking is very simple. If possible, I want to avoid having to 
maintain the canonical and virtual maps. Right now my users only need a valid 
account (e.g. username and password) on my mailserver. That's all that is 
required to access their mailbox over imap, and deliver mail retrieved from the 
isp mailboxes with fetchmail. Their real email address is entirely their own 
responsability. They can easily change it, use more than one, etc without having 
to adjust any server configuration file at all.

Jef

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