High-Inbox B2B Emailer Build

I need a custom bulk-mailing solution that can reliably push 50–100 k cold B2B And messages per day straight into recipients’ inboxes, not the spam folder. The application must run from a clean, secure... (Budget: £250 - £750 GBP, Jobs: Email Marketing, HTML, Mailchimp, MySQL, Node.js, PHP, PostgreSQL, Python, SMTP, Web Development)