Infrastructure recipe
1,000 cold emails a day, mixed Google and Microsoft list
The volume where splitting the fleet starts to pay: a Google pool and an Azure pool, matched to the recipients.
1,000 sends a day needs 219 inboxes across 17 domains, costing $490 a month — prewarmed, sized for a list that is 50% Google, 30% Microsoft and 20% other. That is 22,220 sends a month across 22 sending days.
The pools
- Google Workspace — 650 sends/day from 44 inboxes across 15 domains, at 15/day each and 3 per domain. $352/month.
The 50% on Google, plus the 20% on everything else - Azure — 350 sends/day from 175 inboxes across 2 domains, at 2/day each and 100 per domain. $138/month.
The 30% on Microsoft 365 and Outlook
Right for
The common case: a bought or scraped B2B list that splits roughly half Google, a third Microsoft. This is the shape most agencies are actually running.
Wrong for
A list you have not segmented. The whole recipe depends on knowing the split, and guessing it wastes whichever pool you undersized.
In the sequencer
Two campaigns, not one. Segment the list by recipient MX first, then point the Google segment at the Google inboxes and the Microsoft segment at the Azure inboxes. One mixed campaign across both pools throws away the only reason to have built two.
Why these numbers
The 20% of recipients on neither Google nor Microsoft ride the Google pool. There is nothing to match them to, and splitting a third pool for them would cost more than the matching is worth.
The two pools look wildly different because they are. Azure mailboxes are planned at 2 sends a day each and pack 100 to a domain, so 350 sends needs 175 of them across 2 domains; Google is 15 a day across 3 per domain. The Azure count looks alarming and is cheaper per send — $138 against $352 for roughly half the volume.
Matching the recipient ecosystem is one of the larger levers available, and it is the reason to tolerate running two pools. Google-to-Google and Microsoft-to-Microsoft both clear filters that the crossed pairing does not.
Nothing here reserves capacity. Both figures are the rounded-up minimum, so a pool with mailboxes paused is a pool sending under target.
No reserve capacity is included beyond rounding up. Measure your own recipient mix →