The Rich Text Format (RTF) File Type (Deprecated) recognizes the .rtf file extension.
You can configure some aspects of SDL file types in
.If you want to use WorldServer 11.3 with SDL Trados Studio 2017 SR1 CU8 or later, configure the text/rtf MIME type in WorldServer, as well as any other MIME type that processes RTF assets, to use the new version of the RTF file type instead of the deprecated one.