Wednesday, April 7, 2010

Another life

Unknown     Wednesday, April 07, 2010     No comments
Since known that Titan (the largest moon of Saturn) has a hydrological cycle that is very similar to earth with a bit of a big difference where the hydrological cycle on Earth involve water, while the Titan include hirokarbon which in this case is methane, then I think a little naughty. Possible that Earth and Titan are two of the same world with a lot of difference?

My naughty mind then wandered away to wishful thinking about life. Could there be life in common with many differences as depicted in the hydrological cycle of Earth and Titan? Especially when it aired that Nasa has ever found life in a place that does not allow the existence of life. The most recent information describing caught on a shrimp that live in extreme environments in the northern hemisphere. Some previously existing information jeis-crustacean species which can survive in extremely hot environments. In a very toxic environment.

This information then led me into a little upset. My naughty little show invited me to rethink the definition of life on other worlds in the cosmos. If there are clouds on Titan could be like on Earth, there could be similar to rain on the earth, can exist on Earth-like lightning. There is a similar wind on earth. All the similarities were only different in that the water is not H20 but C2H2D. Temperatures there also reached -170 C. If it is said that the environment does not support life on Titan, are we not to re-think that the difference of the similarity of titan with the earth's life could also support life? Although it differs with the earth. It could be life there is not need 02 but precisely ethane, or nitrogen instead? Maybe there's life on planet Earth is considered hell. Very hot. Only God knows.

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Tuesday, April 6, 2010

Client host rejected: cannot find your hostname

Unknown     Tuesday, April 06, 2010     No comments
'Client host rejected: cannot find your hostname', pesan ini muncul dan cukup banyak yang mengeluhkan (baca: meributkan) beberapa hari terakhir ini, ketika sambungan internet di kantor diganti dan mikrotik juga diganti.
"Pak, ini imil dari si anu kok gak bisa masuk ya!?"
"Pak, ini imil dari si itu juga kok gak bisa masuk ya!?"
Mumet. Wong sebelumnya gak pernah ada masalah begini kok ujug-ujug bin tiba-tiba ada muncul mangsalah beginian. Akhirnya "Coba temennya suruh kirim tolakan imilnya ke saya..."
Yup, itu cara paling gampang dan ringan buat nge-trace. Daripada harus melototin log yang seabreg, mending langsung cari pokok masalahnya. Dan ternyata, ya itu tadi, 'Client host rejected: cannot find your hostname'
Aku gugal-gugel cari tahu sama paman gugel akhirnya didapet kesimpulan bahwa itu adalah sistem proteksi dari mail system untuk menghalau spammer. Jadi setiap imil yang diketahui terkirim dari server yang DNS record nya gak valid, sama mail system kantor bakal ditolak, karena dianggep sepamer. Nah lo.... Memang ini sangat efektif, karena virus-virus yang suka nyepam biasanya bakal menggunakan komputer hostnya langsung untuk merelay e-mail dan ngirim sepam kemana-mana. Tapi, ada tapinya nih; ada beberapa server yang didedikasikan sebagai mail server nyatanya juga gak punya DNS record yang valid. Lha, trus gimana? Kan gak etis kalo kita ngasih tahu sama contact kita kalo mail server mereka tertengarai sebagai spammer. Hmmm... akhirnya, ya udah kita rubah policynya.
Berhubung di kantor make Zimbra maka tinggal masuk ke Admin Control Zimbra masup ke Admin UI nya, trus pilih menu gombal, eh salah, Global Settings, pilih tab MTA. Nah di tab ini, pada groups Protocol Checks pastikan semua check box di group ini dalam kondisi checked (true). Kemudian di Group DNS checks pastikan Check Box 'Client's IP address (reject_unknown_client)' tidak di-check (false), Check Box 'Hostname in greeting (reject_unknown_hostname)' tidak di-check (false), dan Check Box 'Sender's domain (reject_unknown_sender_domain)
' dalam kondisi checked (true). Kemudian klik 'Save'. Dan untuk memastikan konfigurasi telah efektif, coba masup ke server console melalui putty sebagai user 'zimbra' dan jalankan perintah berikut:

zimbra@mail>zmprov gacf | grep zimbraMtaRestriction

hasilnya:

zimbraMtaRestriction: reject_invalid_hostname
zimbraMtaRestriction: reject_non_fqdn_hostname
zimbraMtaRestriction: reject_non_fqdn_sender
zimbraMtaRestriction: reject_unknown_sender_domain

Monggo dipun coba....

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