Warming up
There's no single official number — Gmail and Microsoft 365 judge volume dynamically against reputation. Here are the safe daily ranges by mailbox age, and how to ramp without tripping spam filters.
"How many cold emails can I send a day?" has no fixed answer, because the real ceiling is reputation, not a published number. What follows are safe working ranges by mailbox age and warmup status, and how to scale past them by adding mailboxes instead of pushing one past its limit.
Treat these as ceilings to approach gradually, not day-one targets. A mailbox that jumps straight to 50 sends with zero sending history reads as suspicious regardless of what the provider's raw limit allows.
If you need 300 sends a day and a healthy mailbox tops out near 50, the answer is six warmed mailboxes rotating sends, not one mailbox pushed six times past its safe ceiling. Each mailbox stays under its own limit; the campaign hits its target volume; no single inbox looks anomalous to the provider.
If you run three mailboxes on the same domain each sending 60 cold emails a day, Gmail sees 180 emails a day from that domain, not 60 — keep the domain total under roughly three times what a single warmed mailbox handles comfortably. Gmail is primarily reputation-signal-driven; Outlook is more IP-reputation-driven and tolerates moderate steady volume better than it tolerates spikes.
After any break longer than two weeks, treat the mailbox like a recently warmed one and start at 50% of your previous volume.
A mailbox with real sending history — genuine opens, replies, and time spent in the inbox before cold outreach starts — tolerates meaningfully higher volume than an identical mailbox with none. Warmup is what raises the ceiling described above, not a workaround for ignoring it.
It depends entirely on the mailbox's age and warmup status, not a fixed number. A brand-new mailbox should start around 5–10 a day; a warmed, established one can typically handle 40–50. Provider technical limits are much higher than either figure — reputation-based filtering throttles you long before you hit the platform's actual cap.
Match the pace to your mailbox's warmup status, not the size of the list. Sending a large new list all at once from a cold mailbox is the fastest way to trigger spam filtering — spread it across warmed mailboxes and a ramping schedule instead.
Open and reply rates drop, bounce rate climbs, and providers start routing your mail to spam or throttling delivery silently — often with no bounce or error to alert you. Repeated overuse can get a domain flagged for an extended period. Backing off volume and resuming a slower ramp usually recovers it.
Several. Once your target volume exceeds a single warmed mailbox's safe ceiling (commonly 40–50 a day), add more warmed mailboxes and rotate sends across them rather than pushing one mailbox past its limit.
Roughly 20% more per week, not per day. Watch Postmaster reputation and seed placement at each step — if either degrades, pause and hold at the current level before continuing.
Run a free deliverability check on your sending domain — SPF, DKIM, DMARC, and spam-trap risk — before you send another outreach sequence.
Warmerly warms every mailbox you send from and paces your volume automatically, so you can add sending capacity instead of pushing one inbox past a safe limit. Start free.