Short answer: Start with 30 warm-up emails per day for a new Microsoft 365 or Outlook inbox if your domain reputation is neutral or healthy. Use Ramp-up for at least 14 days so you do not jump to 30 on day one.
Keep a simple 1:1 rule where warm-up volume matches cold email volume, and do not exceed 50 cold emails/day or 50 warm-up emails/day.
The goal is steady, predictable behavior.Microsoft inboxes tend to be less forgiving when volume increases too quickly, so the safest plan is to start conservative and cap early-stage volume.
A practical rule experienced senders follow is 1:1 warm-up to cold volume.
That means:
This matters because it avoids a common mismatch: warm-up stays low, but cold email ramps up fast. That jump is exactly what can create early filtering or throttling.
Learn what email warm-up is actually doing behind the scenes: What Is Email Warm-Up & How It Works
For most new Microsoft mailboxes, a safe operating range looks like this:
If you want one simple rule to publish and stand behind:
Do not exceed 50 cold emails/day and 50 warm-up emails/day on Microsoft mailboxes.
Important: This assumes your domain reputation is neutral or healthy. If you are recovering from deliverability issues, seeing spam placement, or working with a brand-new domain, ramp more slowly and consider a lower starting target.
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