Here some code to get the actions and then the ISaveData. I think that you can use IMailer instead of ISaveData.
Here the implementer
but I agree it is quite obscure how to set things, maybe action.body_post?
So it would be:
from collective.easyform.api import get_actions
from collective.easyform.interfaces import ISaveData
self.context = EasyFormForm(self.context, self.request)
form = self.context.context
for action_id in get_actions(form):
action = get_actions(form)[action_id]
if IMailer.providedBy(action):
action.body_post += "\nPlease check, bla bla… "