I just installed MailButler v.4819 (2130671) for macOS and used MailButler to create a reminder from an email in the Apple Reminders app. That part worked as expected on my Mac, but on my iPad, I receive a notification from the Reminders app as well as the iPad Mailbutler app. I do like getting notifications from MailButler on my iPad when emails are opened (and don’t want to stop those), but getting reminder notifications from Mailbutler on the iPad is redundant.
There needs to be a way to prevent reminder notifications coming from the MailButler iPad app if they're already coming Apple Reminders or another reminder/todo app.