This rings true. A previous job I had did email analytics for the investment banking industry (from boutique firms up to the largest banks in the world). I kid you not, the single biggest driver of our success was the simple fact that our expertise in email meant that we fixed problems that almost all these firms had with email deliverability (bad IPs, SPF/DKIM/DMARC, broken unsubscribe functions, etc) over the actual product itself. This was in our best interest as our product was useless unless recipients could get email delivered to those that wanted it, but it was eye opening.