Shields caps inboxes at 20 sends, runs 120 for 2,400 a day
A client asked why he could not just send from his own Gmail, and Shields published the arithmetic.
James Shields says he caps every sending inbox at 20 cold emails a day, and that a client who wanted 2,400 sends a day therefore needed 120 inboxes spread across 40 domains, three inboxes each.
The post started with a client question, which was whether the campaign could just run from his own Gmail. Shields' answer is that Gmail and Outlook watch how many emails a single inbox sends, and that going much past 30 cold emails a day starts pushing you to spam. He caps at 20 to stay under that line, then divides. 2,400 divided by 20 is 120. None of those inboxes sit on the client's real domain, and the client's main inbox never touches the sending at all.
The numbers he put on it
Shields puts the campaign at about 50,000 emails a month and 18 booked calls in the first 30 days. He does not break out reply rate, list source or vertical, so the only conversion figure available is those 18 calls against roughly 50,000 sends in the opening month.
What the structure costs
The spread is the point. Forty domains is forty things to buy, warm and watch, and Shields treats them as consumable rather than permanent.
That is the trade a lot of senders underprice. One inbox on your own domain is cheap to run and expensive to lose, because when it goes you are rebuilding the address your customers already reply to. A hundred and twenty throwaway inboxes are the opposite, more overhead every week and no single point of failure.
For people sending, the 20 and 30 figures are Shields' operating rule, not a published limit from Google or Microsoft. Neither provider publishes a cold email per day threshold, and Shields does not cite one. What he is describing is the margin he chooses to leave himself, with 20 sitting a third below the line where he says he has seen problems start. Treat it as one practitioner's setting rather than a number you can point at in documentation.
The arithmetic travels even if your cap does not. Pick the per inbox number you trust, divide your target daily volume by it, and that is your inbox count. Then decide whether you want to maintain that many domains, because the infrastructure bill and the warming work scale with the divisor, not with the campaign. Shields' full breakdown is the arithmetic and nothing else.
if one burns we bin it and swap in a new one