· 5 min read
How fast can a new mailbox send? Ramping up without burning it
Why new mailboxes need to start slowly, a sensible ramp schedule, and the signals that tell you to back off.
A brand-new mailbox has no history. To Gmail and Outlook, a mailbox that sends nothing for its first week and then 200 cold emails on Monday looks exactly like a compromised account. The fix is boring and effective: start small and grow slowly.
Why volume spikes hurt
Mailbox providers judge a sender by its behaviour over time — how much it sends, how often recipients open, reply, ignore or mark it as spam, and how many addresses bounce. A new mailbox has no track record, so a sudden spike is all they have to go on, and it looks bad.
A sensible ramp
There's no official number, but a conservative schedule for a new Google Workspace or Microsoft 365 mailbox looks like this:
| Week | Cold emails per day |
|---|---|
| 1 | 5–10 |
| 2 | 10–20 |
| 3 | 20–30 |
| 4 and after | 30–50 |
Many experienced senders stay around 30–50 cold emails per mailbox per day for good, and add mailboxes to grow volume instead of pushing one harder.
Spread sends across the day
Fifty emails sent in the same minute look automated because they are. Leave a gap of a few minutes between sends, and keep an hourly cap as well as a daily one.
If the same mailbox is in several campaigns, the limit has to cover all of them together. Three campaigns at 40 a day each is 120 a day from one mailbox.
Signals to back off
Slow down — or pause — when you see:
- Bounces above about 2%. Usually a list problem; see what's a safe bounce rate.
- Replies dropping to zero on a campaign that used to get them, which can mean you're landing in spam.
- Sending errors from the provider, such as rate-limit or authentication failures.
What about warm-up networks?
Warm-up services exchange automated emails between many mailboxes to build engagement. They can help a new mailbox, but they don't replace a clean list, correct DNS and sensible volume — and some providers dislike artificial engagement. Get the basics right first.
How Outsquid handles it
Every mailbox in Outsquid has daily and hourly limits and a gap between sends, counted across all campaigns. New mailboxes start with a slow ramp that grows day by day and backs off by itself when bounces or failures appear. You can see the limit in force on each mailbox.