Postfix isn't a marketing email tool. It's a general-purpose MTA. Thunderbird isn't a marketing email tool. It's a desktop email client. These are not at all an

Postfix isn't a marketing email tool. It's a general-purpose MTA. Thunderbird isn't a marketing email tool. It's a desktop email client. These are not at all analogous. And you're continuing to ignore the distinction between a tool that is commonly used to send spam even though that's not its purpose, and a tool whose purpose is to send spam. MailChimp is the former, but you're treating it like the latter.