SYMPTOM:
In Strategy Web, the Compress contents option is not available to be enabled when either editing or creating a new email subscription.
CAUSE:
The Enable compression project setting is disabled.
ACTION:
Follow the steps below to enable this setting for the desired project:
1 - In Strategy Developer / Desktop, log into the Project Source.
2 - Right click on the desired project, go to Project Configuration > Deliveries > Email Delivery > Compression.
3 - Check the Enable Compression option, define the Level of compression and the Extension of compressed file options, as shown:

4 - Restart Strategy Intelligence Server.
NOTE:
For additional information on another cause of this issue, refer to the Strategy technical note: KB36424: The option "Compress Content" under Distribution Services is unavailable in MicroStrategy Web 9.x.