Send attachment in message .Net

The error message said "unsupported media type". What type of media content was the attachment?

Here are those supported content types:

• Images: jpg/jpeg, png, gif, bmp, tif/tiff
• Videos: 3gp, mp4, mpeg, flv, wmv, mov
• Audio: mp3
• Files: vcf/vcard, zip, rtf, html

Yes, I have followed above formats. Before It take place error, I still send image whose format is .jpg and it's successfull but when I create another app and install your library so it take error.

png files should not be a problem as it is under allowed file type which means you can send png as attachment.

Pls make sure your file name is correct and don't contains special characters.

Also pls post the full stack trace for better visibility.