Scaling cold email beyond 5k/day without nuking domains

I run a deliverability agency. We push 50k+ emails/day for 20+ clients, manage hundreds of inboxes/domains—and still avoid blacklists.

Here’s what works at 5k+ sends/day:

•	Stick to basics: compliance (DMARC, GDPR, CAN-SPAM, unsub links), list validation, plain-text sends, no tracking, inbox rotation, reasonable limits.

•	Diversify ESPs: don’t rely on Google/Microsoft alone. Always spread across at least 2.

•	Scale horizontally: more inboxes, fewer sends per inbox. Never more than 3 inboxes per domain unless you’re on custom SMTP.

•	Watch rep like a hawk: check spam complaints (>0.1%), placement (<80%), bounces (>3%). Pause + rewarm if you cross thresholds.

•	Use multiple checks: no tool tells the whole story—triangulate inbox health with several.

TL;DR: Deliverability = not just where you put your eggs, but how carefully you place them.