How to set up custom warmup schedules for multiple domains in Warmbox

If you’re managing more than one email domain and worried about landing in spam, you’ve probably heard that “warming up” your inboxes is essential. The problem? Most tools push cookie-cutter schedules and vague promises. If you want to create custom warmup schedules for each of your domains in Warmbox, this guide will show you how to do it right—without wasting time on hype or guesswork.

This walkthrough is for folks who actually care about deliverability, don’t want to play whack-a-mole with blacklists, and are ready to set up something once and let it run (with the occasional tweak). Whether you're running cold outreach, newsletters, or just hate seeing emails vanish into the void, keep reading.

Why Custom Warmup Schedules Matter (and When to Skip Them)

Let’s get this out of the way: not everyone needs a custom warmup schedule. If you’re sending a few emails a day from a single domain, the default settings in Warmbox are fine. But if you’re:

  • Managing multiple domains or brands
  • Scaling up cold email or outbound campaigns
  • Recovering from past deliverability issues
  • Using new or aged domains with different sending reputations

...then setting up custom schedules is worth your time.

What’s the risk of skipping this? Generic warmup can make your domains look similar to each other (not natural), ramp up volume too quickly, or not match your actual needs. That’s how you end up in spam folders—or even on blocklists.

If you’re here for best practices or “industry secrets,” sorry. There aren’t any shortcuts—just attention to detail and a willingness to monitor results.

Step 1: Prep Each Domain Before You Touch Warmbox

Don’t jump into Warmbox yet. If your domains aren’t configured properly, no magic schedule will save you. Before setting up warmup:

  1. Set up DNS records: Make sure SPF, DKIM, and DMARC are correctly set up for each domain. Use tools like MXToolbox or Google Admin Toolbox to check.
  2. Create real inboxes: Don’t just spin up a bunch of throwaway accounts. Use the actual sender addresses you’ll use later.
  3. Don’t reuse blacklisted domains: If a domain is already on a major blocklist, fix that first or start fresh.

Pro tip: If you’re not sure your DNS is right, fix that first. 90% of warmup “failures” are really DNS issues.

Step 2: Add Your Domains and Inboxes to Warmbox

Once your domains are ready, log in to Warmbox. You’ll need to connect each inbox you want to warm up. Here’s how:

  1. Go to the “Inboxes” or “Domains” section (depends on Warmbox’s latest UI updates).
  2. Click “Add Inbox” or “Add Domain.”
  3. Follow the prompts: Usually, you’ll enter your email address, choose your provider (Google, Outlook, custom SMTP/IMAP, etc.), and authenticate.
  4. Repeat for each domain/inbox you want to warm up. Don’t rush—double-check everything as you go.

Heads up: If you’re adding more than 5-10 inboxes, pace yourself. Sometimes authentication limits or provider throttling can trip you up if you add too many at once.

Step 3: Skip Default Schedules—Create a Custom Warmup for Each Domain

Here’s where most people mess up: they use the same schedule everywhere, or just click “Start” and assume it’s handled. If you want each domain to look natural and avoid patterns, set up unique schedules.

Here’s what to do:

  1. Go to the Warmup Settings for Each Inbox

  2. After adding your inbox, find the “Warmup Schedule” settings (sometimes under “Settings” or “Warmup”).

  3. Choose “Custom” Instead of “Default”

  4. Warmbox usually offers a default warmup plan. Ignore it. Look for a “Custom” or “Advanced” option.

  5. Set Your Own Parameters

  6. Start volume: For a brand-new domain, start at 2-5 emails/day. For an aged but inactive domain, maybe 5-10.
  7. Daily increase: Add 2-5 emails per day. Go slower for brand new domains; go a bit faster (but not crazy) for old domains with a clean history.
  8. Max volume: Don’t aim for hundreds of daily warmup emails. Your max should be less than your eventual sending volume, and rarely more than 40-50 emails/day per inbox.

  9. Schedule duration: Plan for 3-6 weeks minimum, longer if you’re especially cautious or had past issues.

  10. Stagger Start Dates

  11. Don’t start warmup for every domain on the same day. Spread them out over several days. This helps avoid patterns that look unnatural to email providers.

Real talk: If a tool lets you set “aggressive” or “turbo” warmup modes, ignore those. Faster isn’t better—you want gradual, realistic patterns.

Step 4: Fine-Tune Warmup Actions (Replies, Stars, Archives, etc.)

Warmbox simulates real user actions (opening, replying, starring, moving emails) to make your sending look legit. Here’s how to get the most from it:

  • Enable replies for at least some warmup emails. Don’t overdo it—20-30% reply rate is more believable than 100%.
  • Mix up actions: Let Warmbox randomly star, archive, and mark as important some messages.
  • Change up timing: Use randomization features if available, so emails don’t always send at 9:00 am sharp.

Ignore: Features that promise “AI-driven engagement” or claim to “guarantee inbox placement.” No tool can promise that. What matters is slow, steady, and human-like activity.

Step 5: Monitor Progress and Adjust

Setting up warmup isn’t “set it and forget it.” Here’s what to watch:

  • Check the Warmup Report: Warmbox gives you stats on sent/received, open/reply rates, and—sometimes—spam/junk folder placement.
  • Look for red flags: If you see sudden spikes in spam placement, drops in reply rates, or lots of bounces, pause and investigate. Could be a DNS issue, a flagged domain, or provider throttling.
  • Adjust schedule if needed: If everything’s smooth, stick to your plan. If not, slow down the ramp-up or even pause for a few days.

Pro tip: Don’t obsess over daily fluctuations. Focus on trends over weeks, not days.

Step 6: “Graduating” from Warmup—What’s Next?

Don’t yank a domain off warmup the day you hit your max volume. Here’s what works better:

  • Maintain a low-level warmup: Keep 10-20 daily warmup emails running even after you start regular sending. This helps maintain reputation.
  • Gradually increase real sending: Don’t go from 0 to 1,000/day overnight. Build up over days or weeks.
  • Keep monitoring: Deliverability is a moving target. Stay alert for changes.

What to skip: You don’t need to keep ramping up forever. Once your domain is “warmed up” and your real sending is stable, the heavy lifting is done.

Honest Takes: What Works, What Doesn’t, and What to Ignore

  • Works: Custom schedules tailored to each domain’s age, history, and actual use. Slow, steady increases. A mix of actions (not just sending, but replying and engaging).
  • Doesn’t work: Copy-pasting the same schedule to every domain. “Turbo” modes. Ignoring DNS issues.
  • Ignore: Overly clever features that sound too good to be true. “Guaranteed inboxing” is a marketing phrase, not a real thing.

If you run into issues, 90% of the time it’s either a DNS/authentication mistake, or you’ve ramped up too fast. Take it slow, fix mistakes, and don’t expect miracles.

Keep It Simple—And Iterate

Custom warmup schedules sound fancy, but the real secret is just being methodical and paying attention. Don’t overcomplicate things. Get your basics right, set realistic schedules, and watch how things go. If deliverability tanks, pause and rethink—don’t just pile on more warmup.

Remember, email providers are always changing the rules. What worked last month might shift, so tweak your approach as needed. Above all, keep things simple and don’t get sucked into the hype.

Happy (and safe) sending.