How to Set Up Warm Email Systems

I had a call with Manny Adelstein to help with Clay's email infrastructure and this is what we talked about. Most people underbuild their outbound infrastructure. They buy 3–5 domains, warm them up, and hope deliverability holds. But if you’re serious about scale, that’s not enough. Here’s what we’ve learned running high-volume outbound: If you want to send 1,000 emails per day, you need the capacity to send 3,000. Why? Because domains burn. Even if your copy is clean and your targeting is perfect, some emails will hit spam. On average, a domain lasts ~2 months before you need to rotate it. So we use a three-set system: Set 1: actively sending Set 2: fully warmed and on deck Set 3: aging in the background When Set 1 gets tired, you switch to Set 2, start warming Set 4, and keep going. The machine never stops. Here’s the tip most people miss: buy domains early and let them age. Even if you’re not using them yet, aging them means when you need new inboxes, you’re not starting from scratch with a zero-trust domain. We buy hundreds (sometimes thousands) of domains when there are sales. Right now, Dynadot is running a promo: .coms for $7 and .cos for $2. We’ll grab thousands and let them sit—no inbox cost until we need them. Use Zapmail.ai and Hypertide.io for inbox setup. They give you admin access, don’t mix your domains with shady senders, and plug right into SmartLead. Don’t wait until deliverability drops to prepare. Stockpile aged domains now, and you’ll always be ready to scale or recover—without missing a beat. I know some people will say, "If you send good emails, you don't need to do this." We just had someone with literally an 8% reply rate which 80% of them being positive go from an 8% reply rate to 1% because of people still marking them as spam. I wish it wasn't this way either, but this is just what we have seen that we have to do.

I've said this before and I'll say it again — we've been struggling.. with cold email deliverability. Cold email infrastructure is frustrating - even when following best practices, deliverability remains inconsistent. I researched everything to solve this problem once & for all. Let me break down what actually works: 1) Infrastructure & Setup: -> Domains & inboxes - Never send cold from your primary domain - Use 3-5 sibling domains, 3-5 inboxes each - Keep branding believable; avoid spammy TLDs (.tk, .ml) - Set up Google Workspace or M365 for legitimacy -> Authentication - SPF covers every sender, DKIM at 2048-bit minimum - DMARC from p=none → quarantine once stable (never jump to reject) - Alignment across From/Return-Path is non-negotiable - Test with mail-tester.com weekly -> Compliance - Clear opt-out, real physical address, legitimate interest docs (EU) - Honor opt-outs within 24 hrs max 2) Sending Strategy: -> Warm-up - New domains need 8-12 weeks minimum - Simulate real engagement (opens/replies/forwards) - Use warmup tools like mailwarm, lemwarm or Instantly.ai -> Volume & Pacing - Start 10-20/day per inbox, add +20-50 weekly if metrics stay green - Randomize send windows; 60-120s gaps b/w sends - Respect recipient time zones (9am-5pm local) -> Timing - B2B sweet spots: Tue-Thu late morning & early afternoon - Avoid Mondays (inbox overload) & Fridays (weekend mode) 3) Content & Copy: -> Subject lines - 6-10 words, human and specific - Personalized context beats cleverness every time - Avoid fake urgency, ALL CAPS, excessive punctuation!!! - Test: "Quick question about [specific company pain point]" -> Body - Short, skimmable, 1 idea + 1 ask maximum - Personalize in layers: hyper-custom for top 10%, segment-level for rest - Use natural language, avoid marketing speak - Images and links kill deliverability - use sparingly -> CTA - Make next step tiny (15-min scan, 1-question reply, "worth a chat?") - Single CTA only - multiple options confuse and reduce response 4) List & Data: -> Sourcing - Prioritize intent and fit over volume always - Dedupe domains (max 1-2 people per company per campaign) - Use Apollo, ZoomInfo or Clay for verified contacts -> Hygiene - Verify syntax + domain + mailbox before sending - Remove hard bounces instantly (never retry) - Prune unengaged cohorts quarterly - Never recycle unsubscribed contacts -> Segmentation - Hot/Warm/Cold bands by recency + engagement - Throttle "Cold" segments heavily 5) Monitoring & KPIs: - Delivery rate ≥98%; investigate anything <95% - Bounce rate <2% (≤1% is excellent) - Spam complaints <0.1% absolute ceiling - Track domain/IP reputation, blacklist status weekly - Use seed accounts & inbox tests ps. Have a response/POA for objections like “not the right person” / “not decision maker” / “No longer at company” / “have in-house team already” / “please contact john from abc” You can also use Valley on LinkedIn - book 2 demos/week for every seat.

“Email isn’t working like it used to.” Sales leaders tell me this all the time. Their teams are struggling to hit quota, blaming email. But a few simple questions reveal why. — Sending from? "Outreach / Apollo / HubSpot" — Main domain? "Yes." — Emails per rep/day? "250." (8-15 reps) — Signature? "1 image, 4 links." — Copy? "Calendar link, hard CTA, use case link." — Who handles deliverability? "No one. IT when accounts get suspended." — Tracking opens/clicks? "Of course! How else would I know deliverability is bad?" — Warming up mailboxes? "What’s warm-up?" — Data source? "Apollo’s "verified" data." 🚩 A major red flag walking. This worked in 2019, maybe early 2023. But now? → ESP filters are brutal → Reps are torching their main domains → Their emails scream automation and get filtered instantly → They’re tracking opens/clicks—metrics that died with Google & Outlook → They’re not even warming up mailboxes → Their data is the same overused, hammered-to-death junk And the worst part? They don’t even realize it. Here’s what actually works: Use secondary domains – Protect your main one. ↳ Buy on Cloudflare Track only replies – Opens/clicks kill inboxing. ↳ Turn off anything that isn't reply rate Cap sending at 30/day per mailbox – More domains, lower volume. ↳ Stop sending too many emails per mailbox/domain Warm up mailboxes ↳ Bare minimum: Instantly.ai. Best: Warmy.io - Email channel. Reliable. Double-verify lists. Bad data = bad reputation. ↳ Use LeadMagic and Emailable Use an SEP built for TODAY’s deliverability – Not outdated playbooks. ↳ Go with Instantly.ai, Smartlead or EmailBison — Cancel Outreach/Salesloft Worried about CRM Data sync? ↳ Let OutboundSync update your Hubspot or SFDC automatically No links. No images. Plain text only. – Avoid spam filters. ↳ Get into the inbox first, that's all that matters Email still works. Just not the way it used to.

New Strategies For Keeping Your Emails Out of Spam 👇 You might be making amazing emails. But if no one sees them, they won’t drive revenue. Step 1: Your Domain Has a Credit Score (And You Probably Don’t Know What It Is) Inbox providers like Google and Yahoo assign a kind of “credit score” to your domain based on how people interact with your emails. Open rates, clicks, replies = build a good credit score → inbox. No engagement, high bounce/spam complaints = bad credit score → spam folder. Use GlockApps to check yours (not a sponsor I just like them). They’ll give you test email addresses, you send a campaign, and they’ll show you exactly where you’re landing (Inbox vs Promotions vs Spam). Goal: You want 75%+ inbox placement. Step 2: Set Up Your Technicals (Takes 5 Minutes) This is non-negotiable. Missing this = guaranteed spam. Make sure the following records are correctly set up: SPF DKIM DMARC If you're using Klaviyo, this is pretty painless and most of it is automated. You just need to manually add a DMARC record (Klaviyo has an article in this if you look it up). Once it's done, it's done forever. Step 3: Warm Up Your Domain (Even If You’ve Been Sending for Years) Think of warming up your domain like building trust with inbox providers. You wouldn’t apply for a $100k loan with zero credit history. Same thing here. If you’re switching domains or have low open rates, treat your list like it’s fresh: Example Warm-Up Cadence: Start with 250 contacts. Then 250 → 500 → 1000 → 2000 Send unique campaigns every other day. Monitor open rates and only scale when engagement stays strong. Even with a massive list, you can get to full sends within 1 month. Step 4: Send Consistently! In 2025, going silent for weeks and blasting your full list out of nowhere is a huge red flag. Set a minimum cadence of 2 emails per week, even if it’s just a simple text-based update. This keeps your domain “active” and builds positive sending history over time. Step 5: Engagement Is Necessary Open rates, clicks, and replies tell inbox providers, “Hey, people actually want this.” Shoot for: 50%+ open rates 0.5%+ click rates <0.1% spam complaint rate Pro tip: If you’re not hitting those numbers, STOP sending to everyone. Instead, build a 30-day engaged segment (people who opened/clicked in the last 30 days) and only send to them. Once you’re consistently hitting 50%+ open rates, expand to 60, 90, 120-day segments. Bonus: Simple Emails = Higher Engagement Fancy designs are cool. But inbox providers love engagement, not aesthetics. Mix in text-based founder emails. Keep buttons clear. Add PS sections. Make it feel personal. It’s not just better for engagement, it builds trust and makes people want to open the next one.

You can craft the most creative messaging and have the best targeting in the world, but if you can't land in the inbox - your efforts will be wasted. I've outlined 8 steps for top notch email deliverability: After reviewing data from 10,000+ inboxes, these are the practices RevGrowth trusts for safe, consistent inbox placement. Most teams skip at least one of these, then wonder why their cold emails land in spam. Here’s how we set up every outbound campaign: 1️⃣ Use Secondary Domains → Never send from your main domain. ↳ We buy secondary domains through Cloudflare for extra security and easy management. 2️⃣ Track Replies Only → Open and click tracking hurt deliverability. ↳ We keep reply tracking on and turn everything else off. Clean signal, less risk. 3️⃣ Send Fewer Emails Per Mailbox → We stick to 30 emails/day per mailbox, max. ↳ Spread your volume across several domains. Fewer red flags, more consistency. 4️⃣ Warm Up Slowly → Ramp up sending volume over time. ↳ Start low, increase gradually. This builds trust with inbox providers. 5️⃣ Double-Verify Your Lists → Bad data kills sender reputation. ↳ We use LeadMagic, Icypeas, and Prospeo.io for initial cleaning, then double-check with BounceBan (Verify risky emails without sending messages). Clean lists = low bounce rates. 6️⃣ Use Modern Sending Platforms → Old-school SEPs drag down deliverability. ↳ We recommend Instantly.ai, Smartlead, or EmailBison. 7️⃣ Automate CRM Syncing → Manual updates cause errors and missed follow-ups. ↳ OutboundSync handles real-time syncing with HubSpot or SFDC. Less manual work, more accuracy. 8️⃣ Stick to Plain Text → Links and images lower inbox rates. ↳ We write text-only emails. They look more human and get better placement. Email is not dead. But the rules have changed. You need the right setup and clean data, not just good copy. I keep these 8 steps in every workflow for all of our client accounts. What’s been your biggest deliverability challenge lately?

Warming up your domain is the most overlooked step in cold email. Here's the 14-Day Rule that's kept our campaigns out of spam folders: Week 1: Send 5-10 emails per day to friends, colleagues, or team members. Have them reply and engage with your emails. Week 2: Gradually increase to 20-30 emails per day. Mix personal emails with light business outreach. After 14 days: Your domain has established sending history and reputation. You essentially want your warmup process to mimic natural email behavior. It shows email providers you're a legitimate sender (instead of a spammer). Obviously, properly warmed domains consistently achieve higher inbox placement rates. The domains we rushed into cold outreach without warmup landed in spam within days. While the ones we warmed up properly maintained strong deliverability for months. This applies whether you're using Google Workspace, Outlook, or any other email provider.

Are your cold emails landing in the spam folder? Here’s how you can solve this issue: You need a little “Email warm-up.” Think of it like preheating your oven. Here’s the recipe: 1. Start small: → Send emails to trusted contacts first. → Think of it like a “Hi” to your favorite barista. 2. Ramp up slowly: → Increase the volume of sending gradually. → It’s like easing into a workout routine. 3. Engage & respond: → Build a rapport with those who open/reply. → Think of them like your gym buddies. 4. Maintain your reputation: → Keep your sender reputation in check. → Monitor bounce rates, review content. → Also use authentication protocols. → Check open rates, click-throughs, responses. 5. Stay consistent: → Be a reliable friend, don’t post & ghost. → And never disappear for weeks at once. Email warm-up helps build your reputation. One audience member at a time. It also helps your emails stand out of the crowd.

One of the biggest hurdles in cold email outreach? Getting into the primary inbox. We send cold emails hoping for replies, but the reality is—it’s nearly impossible to get responses if your emails are landing in spam. I’ve faced this issue myself until I realized there are key steps you can’t ignore to boost deliverability. 𝐇𝐞𝐫𝐞’𝐬 𝐰𝐡𝐚𝐭 𝐡𝐚𝐬 𝐰𝐨𝐫𝐤𝐞𝐝 𝐟𝐨𝐫 𝐦𝐞: ▪️𝐒𝐞𝐜𝐨𝐧𝐝𝐚𝐫𝐲 𝐃𝐨𝐦𝐚𝐢𝐧𝐬 Using secondary domains is crucial for two reasons: → It protects your main domain from being flagged. → It helps distribute the load when sending a high volume of emails. ▪️𝐓𝐞𝐜𝐡𝐧𝐢𝐜𝐚𝐥 𝐒𝐞𝐭𝐭𝐢𝐧𝐠𝐬 Without setting up proper authentication, you’re likely to be blocked. Make sure you configure: → DMARC → DKIM → SPF → MX These might sound technical, but they’re essential for ensuring your emails land in the right place. ▪️𝐏𝐮𝐫𝐜𝐡𝐚𝐬𝐞 𝐚𝐧𝐝 𝐖𝐚𝐫𝐦 𝐔𝐩 𝐌𝐚𝐢𝐥𝐛𝐨𝐱𝐞𝐬 Warming up new mailboxes gradually by sending smaller batches is key. Over time, this builds your sending reputation and helps you avoid the spam folder. Since using Maildoso, I’ve seen firsthand how these steps can be simplified. It automates these processes and ensures that my cold email outreach is efficient and impactful. The 99.9% inbox rate means my emails actually get seen, and my outreach efforts are more productive. How are you solving email deliverability challenges in your campaigns? #ColdEmail #EmailMarketing #Deliverability #BusinessGrowth #Maildoso #MarketingStrategy

Cold email works for B2B SaaS - if you do this. I’ve sent over 1 million cold emails and booked over 3,000 meetings in the SaaS space. The biggest reason I see people give up on it as a channel is: Spam. Our client, Acceleration Broker Sales (B2B SaaS), is the perfect example of this. Before I spoke to them they were seeing zero results from cold email. Then within a couple weeks of doing what I show in this post… They were booking 60 meetings per month on autopilot without paying a single SDR. Here’s how you can swipe exactly what I did for your B2B SaaS: 1. Domains We used an internal automation to generate lookalike domain names, fwd them to the primary domain, and set up inboxes. We set up 2 inboxes per domain (total of 200 inboxes), which allowed us to send approx 3-4k emails per day safely. 2. Sending tools I used Smartlead to warm and send emails. Ideal settings: - After installation of accounts, warm up for 2 weeks. Ideal warmup settings: - Ramp 5 per day - 40% reply - Max 40 emails per day Once warmup is done: - 30 warmup emails per day (no ramp),  - auto-adjust the sending ratio on 20 cold emails per day 3. Implemented basic list hygiene to verify emails. Turned off open/click tracking. Once spam was sorted, we refined their messaging and are booking 60 meetings per month on autopilot. If you think your copy is solid and you’re not seeing results, give this a go and report back. Any questions? Drop them below.