Wrong special german characters in export "Ä,Ö,Ü"

Hi Guys,

One of our user is accessing R/3 system through portal and facing issues with wrong german special characters in export "Ä,Ö,Ü".

When access the same directly in R/3 by logging into SAPGUI, every thing works fine and the issue happens only when access it through portal.

Provide me solutions for this issue.

Best Regards

Venkat