Nah, you're right on the money. That "we landed a Fortune 500 client" line is almost impossible to verify and every outbound agency uses it. The proof has to be in the process, not the headline.
The way I'd pitch it internally: show the whole pipeline from ICP definition through to meetings booked. Lay out the raw numbers - how many contacts you hit, what the reply rate looked like, which messaging variant actually drove conversions, plus the timeline. That kind of transparency gives prospects something they can audit, not just a claim to swallow.
Pilot approach is smarter too. Start a small, low-risk engagement for a few early clients rather than asking them to bet on one big result.
And yeah, the SMTPProvider stuff is more about making sure the backend doesn't fall over once volume scales. Domain setup, bounce handling, sending limits, reputation monitoring - you need that infrastructure in place or the whole machine grinds to a halt. The case study alone won't save you when deliverability tanks at 10k emails a day.
So I'm with you: the proof has to be numbers, process, and a pilot. Nothing else lands.