Auto Response tags not working?

Dear List,

I am not sure %100 It was working previously, when a first time customer 
user (not recorded as customer user in the otrs system) sends a mail to 
the system, auto response can not resolve user's name from the email. I 
tried below three tags in the template but it is still put system 
default email address or display name in to the mail.

Examples:

Thank you <OTRS_CUSTOMER_REALNAME>
Thank you <OTRS_CUSTOMER_From>
Thank you <OTRS_CURRENT_UserFirstname>

All these variables returns something like below,

Thank you [email protected]
or
Thank you Helpdesk

instead of

Thank you Yilmaz Bilgili

---
I am using OTRS 5s on Debian up to date stable system. How can I resolve 
this?

Thanks in advance.

Best regards,
Yilmaz

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