Email Deliverability at Scale: Lessons from Building with Adobe Journey Optimizer

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The Foundation: Sender Reputation—It’s Not Just About the IP

Sender reputation is the score ISPs assign to you as a sender. It’s a blend of your IP reputation and your domain reputation. Both matter—a lot. You can’t just spin up a new IP or domain and blast millions of emails. ISPs are watching, and so are we.

Building a Strong Reputation from Day One

The Critical First Step: IP and Domain Warm-up

Warming up isn’t just for IPs. Every new sending domain or subdomain needs its own careful ramp-up. We built AJO to help you start small—targeting your most engaged recipients first, then scaling up as you build trust with ISPs. Skip this, and you’ll hit blocks or spam filters, guaranteed. The industry’s shifted: domain reputation is now front and center, especially with Gmail and other domain-focused ISPs. Even if your IP is golden, a cold domain can tank your deliverability.

If you want a step-by-step guide to doing this right, check out the official AJO IP Warmup Getting Started page for best practices and workflow details.

How much can you send? With a strong IP and domain reputation, we’ve seen a single dedicated IP handle up to 7.5 million emails per day. But if you try to hit that volume without proper warm-up or with poor engagement, you’ll get throttled or blocked fast.

AJO’s deliverability consultants have access to advanced tools to monitor your IP and domain reputation, and they’ll guide you through the warm-up process to keep you out of trouble.

Reputation is an Investment

If there’s one thing we’ve learned, it’s that reputation is earned over time. Plan your infrastructure, send campaigns people want, and be patient. AJO is built to help you make smart choices from day one, so your investment in reputation pays off with inbox placement and results you can count on.

Authenticating Your Identity: SPF, DKIM, DMARC, PTR

We made sure AJO won’t let you send without proper authentication. Our backend checks for SPF, DKIM, DMARC, and PTR records before you go live with an Email Channel surface, checkout the official Configure Email Channel page. This isn’t just box-ticking—these protocols are your digital passport, proving you are who you say you are.

Maintaining a Stellar Reputation: Signals and Safeguards

Once you’re up and running, the real work begins. ISPs track every bounce, unsubscribe, and spam complaint. Even a 0.1% spam complaint rate can hurt. That’s why AJO automatically manages feedback loops and ensures you honor spam complaints fast. We also keep your lists clean to avoid spam traps—using global suppression lists and our own deliverability experts to spot recycled and pristine traps before they become a problem.

Engagement Signals: What ISPs Really Watch

• Bounces: High bounce rates mean poor list hygiene. ISPs notice.
• Unsubscribes: If people don’t want your mail, ISPs will start to agree.
• Spam Complaints: The fastest way to tank your reputation. Keep it below 0.1%.

Feedback Loops (FBLs): Your Early Warning System

AJO automatically implements and manages FBLs with major ISPs. If someone marks your mail as spam, you’ll know—and you can remove them before it becomes a bigger problem.

Avoiding Spam Traps: The Silent Killers

Spam traps are addresses used by ISPs and blocklist operators to catch spammers. Hit one, and you’re in trouble. There are two types:

- Pristine Traps: Never valid, created just to catch bad actors.

- Recycled Traps: Old, abandoned addresses. If you’re hitting these, your list hygiene needs work.

AJO uses global suppression lists and ongoing analysis to keep you clear of traps and protect your reputation. You can also leverage customer-specific suppression lists to proactively exclude problematic addresses or domains and maintain list hygiene. This means you have control to suppress emails to recipients who bounce, complain, or otherwise hurt your deliverability—before ISPs do it for you (learn more about suppression lists in AJO).

The Interplay of Reputations and ISP Nuances

IP and domain reputations are deeply intertwined. A bad domain can ruin a good IP pool, and vice versa. Gmail cares most about your domain’s history and engagement. Outlook and Yahoo still weigh IP reputation heavily. That’s why we built AJO to give you the flexibility to segment and protect your assets.

Content is King: How Your Message Affects Deliverability

Branding isn’t just a marketing concern—it’s a deliverability lever. Spam filters like SpamAssassin and blocklists like Spamhaus look for consistency and legitimacy. Use branded sender addresses (news@brand.com, security@brand.com) and URLs that match your domain. Every touchpoint should reinforce your identity. If your content or links look sketchy, you’ll get flagged, and both your IP and domain reputation will take a hit.

Strategic Asset Management for Optimal Deliverability

Effective email strategy goes beyond individual campaigns. It’s about managing your sending infrastructure—your IPs and domains—like a pro.

IP Pooling: A Strategic Approach

• By Message Type: Isolate critical transactional emails (password resets, receipts) on one pool and marketing emails on another. Don’t let a bad promo block your password resets.
• By Reputation/Engagement: Create a “premium” pool for your best-performing IPs and most engaged audiences. Keep riskier re-engagement campaigns separate.
• By Region: Pool IPs and domains by region (e.g., europe.brand.com, us.brand.com). This helps with compliance, ISP preferences, and local engagement.

Strategically associating domains and IP pools is key to isolating risk. High-priority or time-sensitive emails should always have their own dedicated pools and subdomains. AJO enforces this by managing separate queues for each unique combination of sending domain, IP pool, and sandbox environment. If one stream gets blocked, your critical mail keeps flowing.

Real-World Examples

Example 1: Multi-Product IP Pooling and Subdomain Strategy

At Adobe, we learned the hard way that mixing traffic is a recipe for disaster. Here’s how we solved it:

• IP Pooling: Dedicated pools for transactional, marketing, re-engagement, and test traffic for each product line.
• Subdomain Delegation: Each product gets its own subdomains, like mail.photoshop.adobe.com for marketing, transact.photoshop.adobe.com for transactional, and so on.
• IP Pool–Subdomain Association: Each subdomain is mapped to the right pool. If marketing for Express gets throttled, it doesn’t touch transactional mail for Sign.

Best Practices:

• Never mix transactional and marketing traffic on the same IP pool or subdomain.
• Use unique subdomains for each product and mail type to isolate reputation.
• Warm up each pool and subdomain separately.
• Monitor engagement and complaints per pool and subdomain.

Example 2: Regional IP Pooling and Subdomain Association

When you’re sending globally, regional isolation is a game-changer.

• Regional Pools: Set up pools like FR-Marketing, US-Marketing, etc., each with their own IPs.
• Regional Subdomains: For France, use mail.fr.adobe.com and transact.fr.adobe.com; for the US, mail.us.adobe.com, and so on.
• Association: Each regional subdomain is mapped to its regional pool. If German ISPs start throttling, only mail.de.adobe.com is affected—not your whole global program.

Best Practices:

• Warm up each regional pool and subdomain separately for the prominent ISPs in the region.
• Use region-specific branding and localization in email content to elevate trust with ISPs.
• Monitor engagement, complaints, and deliverability by region.
• Apply region-specific authentication and compliance policies as needed.
• Isolate risk: issues in one region do not impact others.

References:

- AJO IP Warmup Getting Started

- Suppression lists in AJO