null recipient "@example.com"@example.com accepted

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null recipient "@example.com"@example.com accepted

Matus UHLAR - fantomas
Hello,

I ust received mail where user specified destination address:
@[hidden email]

the mail was accepted and forwarded to "empty_address_recipient",

which docs' say:

"...Postfix does not accept such addresses in SMTP commands..."
http://www.postfix.org/postconf.5.html#empty_address_recipient

however, the address is accepted from remote sites, when I enter destination
domain this way. Even newer postfix versions (3.4.8 checked) accept it.

Should such destination addresses be accepted?

postfix 2.11.3, Debian 8

smtpd_recipient_restrictions = reject_non_fqdn_recipient, reject_unknown_recipient_domain, permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination,

--
Matus UHLAR - fantomas, [hidden email] ; http://www.fantomas.sk/
Warning: I wish NOT to receive e-mail advertising to this address.
Varovanie: na tuto adresu chcem NEDOSTAVAT akukolvek reklamnu postu.
Boost your system's speed by 500% - DEL C:\WINDOWS\*.*
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Re: null recipient "@example.com"@example.com accepted

Matus UHLAR - fantomas
Hello,

Any idea if I can disable these attempts?


On 07.05.20 12:26, Matus UHLAR - fantomas wrote:

>I ust received mail where user specified destination address:
>@[hidden email]
>
>the mail was accepted and forwarded to "empty_address_recipient",
>
>which docs' say:
>
>"...Postfix does not accept such addresses in SMTP commands..."
>http://www.postfix.org/postconf.5.html#empty_address_recipient
>
>however, the address is accepted from remote sites, when I enter destination
>domain this way. Even newer postfix versions (3.4.8 checked) accept it.
>
>Should such destination addresses be accepted?
>
>postfix 2.11.3, Debian 8
>
>smtpd_recipient_restrictions = reject_non_fqdn_recipient, reject_unknown_recipient_domain, permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination,

--
Matus UHLAR - fantomas, [hidden email] ; http://www.fantomas.sk/
Warning: I wish NOT to receive e-mail advertising to this address.
Varovanie: na tuto adresu chcem NEDOSTAVAT akukolvek reklamnu postu.
I don't have lysdexia. The Dog wouldn't allow that.
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Re: null recipient "@example.com"@example.com accepted

Wietse Venema
Matus UHLAR - fantomas:

> Hello,
>
> Any idea if I can disable these attempts?
>
>
> On 07.05.20 12:26, Matus UHLAR - fantomas wrote:
> >I ust received mail where user specified destination address:
> >@[hidden email]
> >
> >the mail was accepted and forwarded to "empty_address_recipient",
> >
> >which docs' say:
> >
> >"...Postfix does not accept such addresses in SMTP commands..."
> >http://www.postfix.org/postconf.5.html#empty_address_recipient

There was a malformed recipient that looked like

        "@some-local-domain"@some-local-damain

See http://www.postfix.org/postconf.5.html#resolve_dequoted_address for
why Postfix looks inside the quotes and tries to deliver to
""@some-local-domain.

With empty_address_recipient=no, Postfix would reject the address
with "unknown user", because there is no user named "@some-local-domain".

        Wietse

> >however, the address is accepted from remote sites, when I enter destination
> >domain this way. Even newer postfix versions (3.4.8 checked) accept it.
> >
> >Should such destination addresses be accepted?
> >
> >postfix 2.11.3, Debian 8
> >
> >smtpd_recipient_restrictions = reject_non_fqdn_recipient, reject_unknown_recipient_domain, permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination,
>
> --
> Matus UHLAR - fantomas, [hidden email] ; http://www.fantomas.sk/
> Warning: I wish NOT to receive e-mail advertising to this address.
> Varovanie: na tuto adresu chcem NEDOSTAVAT akukolvek reklamnu postu.
> I don't have lysdexia. The Dog wouldn't allow that.
>
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Re: null recipient "@example.com"@example.com accepted

Matus UHLAR - fantomas
>> On 07.05.20 12:26, Matus UHLAR - fantomas wrote:
>> >I ust received mail where user specified destination address:
>> >@[hidden email]
>> >
>> >the mail was accepted and forwarded to "empty_address_recipient",
>> >
>> >which docs' say:
>> >
>> >"...Postfix does not accept such addresses in SMTP commands..."
>> >http://www.postfix.org/postconf.5.html#empty_address_recipient

On 13.05.20 10:14, Wietse Venema wrote:
>There was a malformed recipient that looked like
>
> "@some-local-domain"@some-local-damain
>
>See http://www.postfix.org/postconf.5.html#resolve_dequoted_address for
>why Postfix looks inside the quotes and tries to deliver to
>""@some-local-domain.

shouldn't this address be treated as empty and therefore rejected?

at least when resolve_dequoted_address is set to yes (default)

>With empty_address_recipient=no, Postfix would reject the address
>with "unknown user", because there is no user named "@some-local-domain".

isn't empty_address_recipient supposed to be the recipient, so
empty_address_recipient=no just set it to local "no" user?

--
Matus UHLAR - fantomas, [hidden email] ; http://www.fantomas.sk/
Warning: I wish NOT to receive e-mail advertising to this address.
Varovanie: na tuto adresu chcem NEDOSTAVAT akukolvek reklamnu postu.
Fucking windows! Bring Bill Gates! (Southpark the movie)
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Re: null recipient "@example.com"@example.com accepted

Wietse Venema
Matus UHLAR - fantomas:

> >> On 07.05.20 12:26, Matus UHLAR - fantomas wrote:
> >> >I ust received mail where user specified destination address:
> >> >@[hidden email]
> >> >
> >> >the mail was accepted and forwarded to "empty_address_recipient",
> >> >
> >> >which docs' say:
> >> >
> >> >"...Postfix does not accept such addresses in SMTP commands..."
> >> >http://www.postfix.org/postconf.5.html#empty_address_recipient
>
> On 13.05.20 10:14, Wietse Venema wrote:
> >There was a malformed recipient that looked like
> >
> > "@some-local-domain"@some-local-damain
> >
> >See http://www.postfix.org/postconf.5.html#resolve_dequoted_address for
> >why Postfix looks inside the quotes and tries to deliver to
> >""@some-local-domain.
>
> shouldn't this address be treated as empty and therefore rejected?

The RCPT TO address was not empty, and therefore the RCPT TO handler
accepted the address.

There are all kinds of ways that a non-empty address can resolve
to an emmpty address. but the RCPT TO handler does not know that,
and it should not know that.

With resolve_dequoted_address=no, the RCPT TO handler would reject
the address because "@some-local-domain" does not resolve to a
"known" user.

With resolve_dequoted_address=yes, the address resolves to an empty
localpart in a local domain, and is mapped to $empty_address_recipient,
but the RCPT TO handler does not know that, and it should not know
that.

        Wietse