Email subscribers on multisite WP

Hi folks,
We have this plugin installed on a WP multisite at our University and it works really well (thank you!). The one small thing people have commented on is the initial ‘welcome to the group’ email. We’ve had complaints about some of the language used in it.
Obviously, this is easy to change when you know how, but I wondered if it is possible to change it at the site level so that, if people don’t notice they can change the wording, it’s a little more formal? Does anyone know if that’s possible? I can’t see a way to do it but I might be missing something.

Thanks
Karen