Send email notification to a mailing list on form submission

I have created a mailing list with list of users.  I have created a form and in the form settings,  Under "Send email notification for responses to..." section, when I try to add, it is not allowing to add this mailing list.  Screenshot attached.

My requirement is to send a mail to a group of people(list changes periodically-added to a mailing list ) on a form submission. How this can be achieved?

Any help on this is highly appreciated.

Thanks,

Santosh