File extension .stm,STM file extension

A file with the .stm file extension is known as an Exchange streaming media file, a Scream Tracker 2 module or a SSI web page.

STM files store streamed native Internet content. New messages are saved to the STM file on the mail server until they are accessed by a user's mail client. When messages are accessed by a MAPI client, they are transferred to the EDB file and converted to the native Exchange format.
Web page that contains server side includes (SSI); references functions on the server that generates content for the Web page; processed by the server when accessed, which outputs HTML to client's Web browser.

Server Side Include Web pages may also use the .SHTM or .SHTML extensions.

Audio tracker module saved by Scream Tracker 2; contains tracks, patterns, and samples used for instruments that are played back in the songs.

Help how to open STM files:
Use any text editor or specialised application (Adobe Dreamweaver, Contribute). To open use web browser (Internet Explorer, Firefox, Opera)
stm file - HTML server side include file
When a video or email is sent as an attachment to an email address housed on a Microsoft Exchange server, the server saves the file as an exchange streaming media file. When you access your email, the server transfers the .stm file to its original file extension and then sends it to your email, where you can download it.