So, you are live with your Mendix application which sends emails. You are periodically cloning your production database to lower instance to address defects. The problem which you will be facing is that as you are testing defects in lower environment, your Mendix application may keep on sending emails out. This may be a very undesired activity. Your users will be receiving unsolicited email from an application they may not be even aware exists.
Suggest enhancing the module restricting emailing functionality in a non-production environment only to whitelisted email addresses.