before you plan any campaign, you need to know what 100 daily sends actually looks like in infrastructure terms.

most teams skip this step entirely. they pick a target like "let's send 500 a day" and then try to cram it through whatever inboxes they already have, which is how you end up pushing 35 sends per inbox and getting shut down by the weekend.

THE CEILING

keep this rule in mind before we go any further. 10 to 15 sends per inbox per day is the ceiling, and you break it at your own expense.

go above 30 to 40 and you'll see instant account shutdowns. we see it every week on support calls. a customer will tell me everything is broken, we look at the volume, and it's right there: 35 sends a day from a single inbox with no warmup running alongside. the writing was on the wall before they even started sending.

the game now isn't to maximise output per inbox, it's to maximise lifespan per inbox. lower per-inbox volume means inboxes that last 8 to 12 months instead of the old 3 to 4 month ceiling.

THE FORMULA

your daily send target divided by sends per inbox gives you the total inboxes required.

use 10 as the conservative number, or use 15 if warmup health is strong and your sender reputation is already established. every 3 inboxes needs 1 dedicated domain, which is the ratio we run across 250,000+ inboxes in production.

WORKED EXAMPLES

The numbers land like this for four common daily volume tiers.

• 100 sends per day: 10 inboxes at 10 per day (or 7 inboxes at 15 per day) across 3 to 4 domains.
• 250 sends per day: 25 inboxes at 10 per day (or 17 inboxes at 15 per day) across 6 to 9 domains.
• 500 sends per day: 50 inboxes at 10 per day (or 34 inboxes at 15 per day) across 12 to 17 domains.

THE TWO-LANE SPLIT

whatever your inbox count lands on, you split it across Google Workspace and Microsoft 365, running either a 70/30 or a 50/50 configuration. never go all-in on one provider.

teams that rely on only one provider collapse when that provider updates its filtering models. we've watched it happen three times in the last 18 months. teams running 100% Google got wiped in a weekend, while teams running 70/30 still had 30% of their pipeline moving while they rebalanced the rest.

two lanes gives you infrastructure resilience. one lane leaves you one bad policy update away from a dead pipeline.

YOUR TURN (5 minutes)

write down your daily send target: ___