Cold Email Sending Infrastructure Setup

Set up a complete cold email sending infrastructure for an agency. You get 4 fresh domains (registrar access provided) and an Instantly account. Deliverables: Google Workspace tenant(s) with 3 mailboxes per domain (12 total), sender names provided by us Full DNS authentication on all 4 domains: SPF, DKIM, DMARC (start p=none), MX, plus a custom tracking domain per domain in Instantly All 12 mailboxes connected to Instantly with warmup enabled, daily send caps configured (ramp to max 30–50/day per mailbox), sending schedule set to recipient business hours (US East, UK, Australia East) Domain forwarding: each secondary domain redirects to our main site Acceptance test: every mailbox scores 9+/10 on mail-tester.com, screenshots provided Handover doc: all logins, DNS records, what was configured and why, plus a one-page "do not do this" list for keeping deliverability healthy You must have done this exact setup multiple times in 2025–2026 (Google/Yahoo bulk sender rules era). In your proposal, tell me: your preferred DMARC rollout approach, and why you would or wouldn't use Microsoft 365 for this. (That second one is a filter; there's a right answer.)