Mailbox providers keep score on every sender. The score decides whether your next campaign lands in the inbox, the spam folder, or nowhere. You can't read the balance directly, but it behaves so much like a bank account that the metaphor does real work: deposits are small and slow, withdrawals are large and fast, and going overdrawn gets your card declined everywhere at once.
What the account actually is
Two ledgers, kept separately by each mailbox provider: one against your sending domain and one against your sending IP. On a shared ESP plan the IP ledger is co-owned with strangers (their bounces splash on you, and vice versa; this is why ESPs police bounce rates so hard). The domain ledger is all yours, follows you between providers, and is the one worth guarding with your life.
Deposits: small, slow, compounding
- Delivered mail that people open, read, reply to, or rescue from spam. Replies are the premium deposit. Nothing says "wanted" like a response.
- Consistency. Similar volumes at similar intervals from the same domain. Providers trust rhythm; they distrust a domain that's silent for months and then sends 80,000 overnight.
- Passing authentication, every time, on an aligned domain (see the 2026 guide).
Withdrawals: the exchange rates are brutal
Approximate but honest rates, as observed across postmaster data and painful experience:
| Event | Costs roughly |
|---|---|
| Hard bounce | ~10 clean sends' worth of goodwill |
| Spam complaint | ~100+, the single most expensive click in email |
| Spam trap hit | Not a withdrawal: a frozen account pending investigation |
| Sudden volume spike | A fraud alert on your own card |
| Mass deletes-without-reading | A slow leak: small, but on every send |
The asymmetry is the whole lesson: one careless send into an old list can spend a year of good behaviour. A 20,000-send campaign at 6% bounces makes ~1,200 withdrawals at 10x. Twelve thousand sends' worth of trust, gone in an afternoon.
Going overdrawn
There's no single "banned" line; it's a dimmer, not a switch. First your mail starts filtering to spam for less-engaged recipients. Then for most recipients. Then providers start deferring or rejecting outright, and if a blocklist got involved, everyone downstream of it follows. The nasty property of the overdraft: you find out late. Opens sag a campaign or two after the damage, and by the time someone says "check the spam folder", you've been overdrawn for weeks.
Get statements: Google Postmaster Tools (domain reputation, spam rate) and Microsoft SNDS are the closest thing to reading your balance. Free, ten minutes to set up, and the difference between discovering a problem in week one versus month two.
Recovery: slower than the fall, always
Reputation rebuilds the only way it was built: consistent, low-bounce, low-complaint sending, but now with a provider that's watching sceptically. The proven path: clean the list completely (fix the cause first, or you're refilling a leaking bucket), restart at reduced volume to your most engaged segment, and rebuild volume gradually over 2–6 weeks as the good signals accumulate. There is no shortcut, no form to fill in, no support ticket that hurries it. Which is exactly why the cheap insurance, cleaning on schedule, beats every recovery story ever written.
deposits in cents, withdrawals in notes. email's oldest exchange rate ✦
The free evaluation checks a sample of your list end to end and tells you straight whether it needs cleaning. Verdicts in plain English, about ten minutes, no card.
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