E-mail notification for a transaction - how?

We have a workflow configured for the Cancel Work Relationship transaction (BPM), with one of the rules requiring approval. However, we have observed that while the approval requests show up in the bell icon and infolet section for approvers (as expected), a request e-mail is also being sent to those approvers as well. While this isn't a problem, we don't know where configuring the alert e-mail notification is managed. For what it's worth mentioning, it's handy to have the e-mail as transaction approval can be managed there as well. Thank you in advance for any insights.