salam pak syafril

setiap saya kirim email dari koneksi luar memakai program outlook express selalu error. lognya seperti dibawah ini pak.

START Event Log / MDaemon PRO v10.0.3, SMTP (in) log information
-------------------------------------------------------------------------------
Event Time/Date             Event Description
-------------------------------------------------------------------------------
Wed 2009-02-11 12:46:48: Session 2452; child 2; thread 2752
Wed 2009-02-11 12:46:45: Accepting SMTP connection from [114.121.39.207:2316] Wed 2009-02-11 12:46:45: --> 220 variausaha.com ESMTP MDaemon 10.0.3; Wed, 11 Feb 2009 12:46:45 +0700
Wed 2009-02-11 12:46:46: <-- XXXX localhost
Wed 2009-02-11 12:46:46: --> 500 What? I don't understand that.
Wed 2009-02-11 12:46:46: <-- HELO localhost
Wed 2009-02-11 12:46:46: --> 250 variausaha.com Hello localhost, pleased to meet you
Wed 2009-02-11 12:46:47: <-- MAIL FROM:<fr...@variausaha.com>
Wed 2009-02-11 12:46:47: --> 250 <fr...@variausaha.com>, Sender ok
Wed 2009-02-11 12:46:47: <-- RCPT TO:<lak...@variausaha.com>
Wed 2009-02-11 12:46:47: Performing DNS-BL lookup (114.121.39.207 - connecting IP)
Wed 2009-02-11 12:46:48: *  zen.spamhaus.org - failed - 127.0.0.11
Wed 2009-02-11 12:46:48: *  bl.spamcop.net - passed - 127.0.0.11
Wed 2009-02-11 12:46:48: *  zen.spamhaus.org - failed - 127.0.0.11
Wed 2009-02-11 12:46:48: ---- End DNS-BL results
Wed 2009-02-11 12:46:48: 'Recipient unknown' given and connection dropped to divert future spam
Wed 2009-02-11 12:46:48: --> 550 <lak...@variausaha.com>, Recipient unknown
Wed 2009-02-11 12:46:48: SMTP session terminated (Bytes in/out: 99/254)


tapi kalau saya menggunakan koneksi intern, kirim email berjalan lancar. mohon pemjelasannya ya pak.
terima kasih.
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