Error 550

Hello all,

I get this error when try to send mail to my [email protected] from other mail service.
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This is an automatically generated Delivery Status Notification

Delivery to the following recipient failed permanently:

[email protected]

Technical details of permanent failure:
PERM_FAILURE: SMTP Error (state 13): 550 "Unknown User"


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But whet I send mail to [email protected] --all OK.

The user [email protected] -exist I may use squirrelmail to get access to his mail.

I do this http://help.directadmin.com/item.php?id=59 -does not help me.
help.

now all work I was update exim and rewrite conf.