connect to outlook exclude a extension
It will be really important to exclude the extensions of the files you would like to exclude. For example, if you do not want to upload '.docx' files, it will be very important.
Many customers need this to save a lot of space in the cloud.
Peter Groft commented
Outlook uses the Level1Add registry key to permit you to add additional attachment file name extension types that you want to block. To add other attachment file name extension types that you wish to block, you must add the Level1Add key to the registry.