Early release of working software is critical to a successful rewrite. Two-way data exchange can keep both systems working in parallel and reduce risk.
Knowing where you are in the company growth journey can help you identify the real problems you're struggling with and find a solution before you burn out.
Investing in a large, "world-changing" first release is wasteful and dangerous. Successful companies launch a small, valuable product, then start learing.
How can you test that your code triggers the message to be sent AND that the message gets delivered to a real mailbox? With a disposable email service.
When dealing with poor team dynamics, many teams ignore the interpersonal dimension and fall into the trap of adding process. This does more harm than good.