is it a spam relay?

19 Jan 2001


      Please, help me understand this log:
Jan 19 06:51:06 mand sendmail[2353]: GAA02353: ruleset=check_mail,
arg1=, relay=[12.110.33.133], reject=501
... Sender domain must exist

Jan 19 06:53:36 mand sendmail[2355]: GAA02355: ruleset=check_mail,
arg1=, relay=[12.110.33.133], reject=501
... Sender domain must exist

Antal

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