Syafril Hermansyah said the following on 28/06/09 15:58 +07:00:
> On 08/05/09 16:48 +07:00 Syafril Hermansyah wrote :
>> On 15/03/09 23:27 +07:00 Syafril Hermansyah wrote:
>>> > [ harap diperhatikan bhw fitur dan menu yg disebutkan di serial tulisan
>>> > ini berlaku di MDaemon 10.0.4 keatas, di versi sebelumnya fitur/menu
>>> > tsb tidak ada atau tidak jalan sesuai rekomendasi ]
>>
>> Dari pengalaman 3 bulan terakhir mengaktifkan Reverse Lookup, ternyata
>> membuat spam rejection menurun 60% dan pengisian reverse lookup
>> whitelist menurun 70% (dibanding spamfilter whitelist) sementara
>> spamaccepted sedikit meningkat dari 0.05% menjadi 0.55%.
>> Rupanya sudah makin banyak postmaster yg melek teknologi shg sudah layak
>> dilakukan saat ini.
>
> Maaf ada yg terlewat tentang mengurangi false positive (salah duga)
> akibat mengaktifkan Reverse Lookup ini secara penuh.
> Dalam praktek sering terjadi legimate sender (sender domain yg sering
> berkorespondensi dg user kita) akan tetapi masih kurang gaul dalam
> mensetting mail servernya shg belum pernah baca RFC-2821
>
> <http://www.ietf.org/rfc/rfc2821.txt?number=2821>
>
> 4.1.1.1 Extended HELLO (EHLO) or HELLO (HELO)
>
> These commands are used to identify the SMTP client to the SMTP
> server. The argument field contains the fully-qualified domain name
> of the SMTP client if one is available.
> .......
> A client SMTP SHOULD start an SMTP session by issuing the EHLO
> command. If the SMTP server supports the SMTP service extensions it
> will give a successful response, a failure response, or an error
> response.
>
> yg artinya nama server wajib didaftarkan di authoritative DNS, tidak
> boleh seenaknya kasih nama server.
Mohon maaf, kutipannya kurang pas; mestinya lbh cocok yg ini
3.6 Domains
Only resolvable, fully-qualified, domain names (FQDNs) are permitted
when domain names are used in SMTP. In other words, names that can
be resolved to MX RRs or A RRs (as discussed in section 5) are
permitted, as are CNAME RRs whose targets can be resolved, in turn,
to MX or A RRs. Local nicknames or unqualified names MUST NOT be
used. There are two exceptions to the rule requiring FQDNs:
- The domain name given in the EHLO command MUST BE either a primary
host name (a domain name that resolves to an A RR) or, if the host
has no name, an address literal as described in section 4.1.1.1.
> URL ini mungkin lbh jelas jika dibaca
>
> <http://www.spamstopshere.com/blog/2008/05/14/dns-problems-affecting-e-mail-delivery-mailserver-name/>
> <http://www.spamstopshere.com/blog/2008/05/13/dns-problems-affecting-e-mail-delivery-ptr-records/>
> <http://www.spamstopshere.com/blog/2008/05/16/dns-problems-affecting-e-mail-delivery-sender-domain/>
>
> Untuk mengurangi salah duga pada saat Reverse Lookup diaktifkan maka
> lakukan langkah persiapan sbb :
>
> 1. Aktifkan "Insert warning headers into suspicious messages"
>
> http://mdaemon.dutaint.co.id/10.0/index.html?security__reverse_lookup.htm
>
> 2. Buat content filter rule utk catch ignorant sender host
>
> http://mdaemon.dutaint.co.id/10.0/index.html?cf_creating_a_new_content_filter_rule.htm
>
> Rule Name : Ignorant Sender Host
> Conditions : If X-Lookup-Warning header contains .
> Actioons: copy message to \\mdaemon\queues\bad
>
> sementara di reverse lookup menu cukup diaktifkan
>
> [x] Perform PTR lookup on inbound SMTP connections
> [x] Exempt authenticated sessions (lookup will defer until after MAIL)
>
> [x] Perform lookup on HELO/EHLO domain
> [x] Exempt authenticated sessions (lookup will defer until after MAIL)
>
> 3. Secara reguler, misalkan tiap malam hari, periksa isi bad folder dan
> periksa headernya, jika ada header X-Lookup-Warning di message tsb maka
> masukkan IP address legitimate sender host kedalam reverse lookup whitelist.
>
> 4. Setelah 1 bulan, maka Anda akan aman mengaktifkan Perform PTR lookup
> dan Perform HELO/EHLO lookup.
>
>
--
syafril
-------
Syafril Hermansyah
MDaemon-L Moderators, running MDaemon 10.1.0
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