another 550-Verification failed

Hai... i'm new here...
i just found this forum by googling my problem...

i have the same problem with bigwebmaster, but not exactly the same..
my problem is.. when i try to send outgoing email, this error was ocured :



----- The following addresses had permanent fatal errors -----
<abc@somedomain.com>
(reason: 550-Verification failed for <someuser@somedomain01.com>)

----- Transcript of session follows -----
... while talking to pqrs.somedomain02.net :
>>> DATA
<<< 550-Verification failed for <someuser@somedomain01.com>
<<< 550-Called: xx.xxx.xx.xxx
<<< 550-Sent: RCPT TO:<someuser@somedomain01.com>
<<< 550-Response: 553 sorry, your envelope sender has been denied (#5.7.1)
<<< 550 Sender address someuser@somedomain.com does not exist
550 5.1.1 <abc@somedomain.com>... User unknown
<<< 503 valid RCPT command must precede DATA



is it the same case with bigwebmaster?
what should i do first?

thanks before for any help to my problem.
i hope i'll get the answer as soon as possible.


regards,
NewInWeb

Sender verification is failing, that much is clear.

Either your mailhost does not comply with verification, or your specified ID does not exist (as in the case of spammers who use false usernames at domains).

Sounds rational to me.

Hey thanx for ur reply Daemonguy...

but i still don't get it..
i'm sorry...
can u make it more clearly for me?
about what should i do.. so that i can send an outgoing email again and that error won't occured again...

hi
can u please update the mail clinet and control panel program you are running on the server?