Reciever Mail Content to "UTF-8"

Hi Experts

We have an issue with mail triggering from SAP PO which is triggering al the mails as - Content-Type: text/plain due to which our domain mail filtering is blocking the mails.

I have used to take the Content conversion to UTF-8 explicitly, though the mail propertis showing content type as test/plain only.

Can someone please suggest how can we achieve this as by the Mail content should be UTF-8 or Binary.

Thanks

VR