A SESX file is a session file, which is a session file and is used by Audition software. Adobe Audition is a professional audio editing program for editing, mixing and finishing. Audition was called before it was bought by Adobe Cool Edit Pro.
A SESX file only contains information about the files used, but no audio data. Therefore, a SESX file is useless on its own and Audition would crash with an error message when trying to load the non-existent audio data. You always need the audio files referenced in the SESX file. It is also important to save the tracks after a sound recording and not just the session.
Note that SESX files are version 4 (CS5.5) session files that can not be used with older versions.
Most often resolving problems with opening SESX files is very simple. Just install an appropriate program that supports such files. All of the listed programs support SESX files, but may vary in offered function and purpose. Some programs may be capable only of viewing contents of SESX files or offer file conversion options, but may not be capable of editing such files.
It is possible that although a compatible program has been installed on user’s system, it is not used by the system to open it. This may happen because no default application was associated with this type of files. To associate SESX files with given application, select "Open with" from drop-down menu (accessed by right-clicking on the file). Then select from the list the program or application you want to be used to open this type of file. If the Adobe Audition applications is not on the list, select "Browse" option in order to manually locate the directory where Adobe Audition has been installed.
Sometimes problems with opening SESX files may not lie with the application itself, but can arise due to other causes, such as: