Welcome, if you would like to post a comment please register.
We also encourage you to explore all things Zimbra with our team and members of the community.
You can't set zimbraFileUploadMaxSize on the COS or the user. You can set it on the server -- can you run a separate Zimbra server for your no-upload users?
You should also file this feature enhancement request in bugzilla.
At present, you can only set zimbraFileUploadMaxSize at server level. If you run two separate Zimbra mail servers, you can set it differently on each server.
This isn't a good solution, but it does what you want in the absence of zimbraFileUploadMaxSize being settable at COS level.