MailToBotic2 is entirely Apple® sandbox compliant.
If you like to know more about Apple® sandbox technology, go to:apple.com
Those kind of popup windows are completely normal. You need to give access to MailToBotic to talk against other applications.
In this particular case you need to give access to MailToBotic to access Apple Mail®, what is the main reason to run MailToBotic.
REMARK: Those kind of permissions must be given only once, on the first run of MailToBotic.
Afterward, the system knows that you trust MailToBotic.
MailToBotic does not pretend to be a mass mail program for the simple reason that MailToBotic relies on your own email account configuration. For example, depending on the mail provider, you may not send more than 500 emails per day.
But if you have to communicate regularly with several dozen correspondents and, for example, for privacy reasons (GDPR) want to send a separate email to each of them, MailToBotic can be of great help at a very low cost.