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You can have perfect SPF, DKIM, and DMARC records.
You can warm up your domains for weeks.
But if you suddenly send 500 cold emails from a mailbox that’s used to sending 10…
You’ll get flagged...fast.
Mailbox providers (Google, Microsoft, Yahoo) monitor sending behavior patterns. They don’t just care what you send, they care how fast and how much.
When that pattern changes too quickly, algorithms assume something suspicious is happening.
That’s when reputation drops, emails land in spam, and your domain starts losing trust.
Mailbox providers track more than just the number of emails you send.
They evaluate:
The moment your sending pattern breaks the “normal” rhythm, filters start tightening.
For example:
If your mailbox usually sends 20 messages per day, jumping to 200 overnight can trigger flags, even if your content is clean.
A sudden increase in outbound volume signals one of three things to mailbox providers:
Even legitimate senders can get caught in this.
That’s why safe scaling, also known as “warming up”, exists.
Warm-up doesn’t just “prove” you’re real. It teaches mailbox providers what normal looks like for you.
A strong sender reputation builds through gradual, consistent activity.
Here’s an example curve for new outreach domains:
Scaling slowly keeps your signals stable and builds long-term trust.
Once a mailbox consistently performs well (low bounces, strong replies), you can increase volume safely.
For cold email outreach, the Warmup-to-Outreach Ratio is your safety net.
Example:
If you’re sending 30 cold emails per day, you should ideally have at least 30 warm-up interactions happening daily through Mailivery.
That 1:1 ratio balances your reputation by offsetting new cold sends with positive engagement from warm-up activity.
The result: mailbox providers see a healthy pattern of replies, opens, and consistent sending volume, not sudden cold blasts.
Here’s what we see when senders skip the gradual ramp-up:
Even with the right setup, nothing recovers a domain faster than time +consistency. Once trust is damaged, it takes weeks of low-volume warm-up to rebuild.
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1. Start small, scale smart.
Begin at 20–30 emails per mailbox per day, then increase by 10–20%weekly.
2. Monitor your warm-up health.
Use Mailivery’s Health Score and volume chart to track progress.
3. Keep a 1:1 warm-up ratio.
Match every outreach email with a warm-up email until your domain has stable inbox placement.
4. Use multiple domains for higher volume.
Instead of 1 domain sending 500/day, use 5 domains sending 100/day. Spread the risk.
5. Track engagement signals.
If replies drop or opens dip below 50%, pause scaling and focus on warm-up activity again.
Read 25 Email Deliverability Best Practices to Follow in 2025 to learn more about infrastructure, ramp-up, domain setup, and scaling safely.
Volume alone doesn’t get you flagged, inconsistency does.
Mailbox providers reward predictable, authentic senders.
Start slow, maintain engagement, and scale only when your reputation can handle it.
That’s how you reach inboxes at scale, not spam folders.
The easiest way to get responses to your cold emails.
