Returned mail: Data format error

[MAILER-DAEMON]

The original message was received at Sat, 16 Dec 2006 09:08:37 -0500
from linux.cz [195.67.228.53]

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<sendmail na linux.cz>

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... while talking to server linux.cz.:
554 5.0.0 Service unavailable; [117.210.69.182] blocked using relays.osirusoft.com
Session aborted