Hi Mahesh,
Greetings from Syncfusion support.
We have checked your reported query. Currently, we have no any API/ Libraries to extract your specified typed files first page to load it as thumbnail for files in File Manager . You can any public libraries/convertors to extract the first page of your mentioned file type(.msg, .oft, .eps) file and convert it as FileStreamResult to load it successfully as thumbnail image in File Manager.
Similar to this requirement, we have provided a custom sample for extract the first page of pdf, docx type files in our FileManager component and set them as thumbnail image for FileManager component.
Please, check out the following forum link which will help you to achieve your expected requirement.
Please let us know, if you need any further assistance.
Regards,
Sowmiya. P