Former team members still receiving e-mails re issue tracking (BB-3159)

Two former team members are still receiving e-mails regarding issue tracking. It happens whenever I change an issue that was originally created by them.

They've told me to stop these e-mails from being sent. Also, I do not like them to receive updates on these issues.

Can I (or they) disable this? Preferably in a central location so that I don't have to change all the individual issues.