Different Domain Name

The following is an alert triggered based on Security Event ID 529 from the eventlog analyzer on my my Domain Controller. My question is why is my domain controller triggering such log even if the domain name is different which in this case the event log is reflecting "TEOCH1" as the computer domain name while my domain is "XXX"

Host : Domain_Controller_XXXXX
Application : Security
Time Generated : Thu Oct 04 11:10:53 2007

Criticality : Medium
Number of Occurances : 5
Message : Logon Failure:

Reason: Unknown user name or bad password

User Name: teo

Domain: TEOCH1

Logon Type: 3

Logon Process: NtLmSsp

Authentication Package: NTLM

Workstation Name: TEOCH1

Caller User Name: -

Caller Domain: -

Caller Logon ID: -

Caller Process ID: -

Transited Services: -

Source Network Address: 10.81.160.236

Source Port: 1081

This satisfies HIPAA requirement 164.308(a)(5) and SOX Sec 302 (a)(4)(C & D) for Falied logon Attempts