Basically, every employee can delete their own sent messages.
However, with the default settings, the messages would only disappear from their own respective chat window.
To delete messages so that the message is also deleted for the recipients, a custom setting must be made by an administrator.
To do this, navigate in the administration menu to Settings -> Chat, and change the setting Delete message for everyone from No to Yes.
Note that it can take up to 10 minutes for the change of the setting to take effect.
If the setting has been successfully changed, employees can delete their own chat messages retrospectively for everyone up to 30 minutes after sending.
Please wait... it will take a second!