Automated Deliverability Testing with Braze

Why does your Braze email campaign land in spam instead of the inbox?

You’ve polished the copy. The layout’s responsive. The segmentation’s tight. But your campaign still lands in spam—despite Braze’s flawless delivery orchestration.

That’s because Braze handles the sending, not the health of your list. It won’t catch invalid addresses, spam traps, or risky inboxes before they hurt your sender reputation.

Automated email deliverability testing with Braze and third-party verification isn’t a luxury. It’s the only way to ensure your campaigns reach real inboxes at scale—before you send.

Key takeaways

Braze doesn’t validate email list health—you must do it separately to prevent hard bounces and spam complaints.
Automated verification before sending reduces hard bounces by up to 90% in practice, protecting sender reputation.
Combining Braze’s delivery engine with pre-send third-party verification is the only reliable method to achieve inbox placement at scale.

What happens when you send to a list without third-party verification?

You’re risking hard bounces, spam traps, and blacklisting—all before your first email even reaches an inbox. Without verification, outdated, invalid, or suspicious addresses slip through, damaging sender reputation and sinking inbox placement. Major ISPs like Gmail and Outlook use reputation signals to filter mail; one batch of bad sends can trigger automatic suppression. This isn’t theory—it's how deliverability fails in real campaigns.

Hard bounces don’t just waste sends—they hurt your reputation

Every hard bounce you send to a non-existent address is a red flag to ISPs. If 2% of your list bounces, that’s already below industry thresholds for acceptable bounce rates. High bounce rates correlate directly to lower deliverability scores. If you’re sending to 100,000 emails and 5,000 hard bounce, that’s 5%—a level that can trigger filtering or even blacklisting by providers like Spamhaus.

Spam traps kill your sender reputation silently

Outdated lists often include old or recycled addresses—these are spam traps. When you send to them, ISPs flag your domain immediately. Even one spam trap hit can cause long-term deliverability damage. Many spam traps are now actively monitored by abuse departments and blacklisting services, so a single send can trigger automated suppression. According to research from Return Path (now Validity), spam traps are among the most common reasons for sudden drops in inbox placement.

Let's say you're using Braze for customer campaigns. Without verifying your list first, you're relying on Braze’s built-in bounce processing—which only catches problems after the fact. That’s too late. You’re already burning sender reputation by sending to dead or trap addresses.

Inbox placement collapses even with great content

Even if your message is timely and relevant, a poor sender reputation leads to low inbox placement. Studies show that senders with weak reputations are often relegated to spam folders or entirely blocked, regardless of content quality. This means open rates drop below 15%—well below what’s required for campaign success. The cost? Lost engagement, missed conversions, and wasted ad spend.

And because you’re missing automated feedback loop (FBL) integration or third-party validation, issues aren’t detected until after delivery. By then, damage is done. You're chasing reputation repair while still sending to bad addresses.

If you're not verifying emails before sending through Braze—or any platform—your campaign is already at risk. MailTester gives you real-time verification and inbox placement tests to catch these problems before they start. Test your list, validate addresses, and send only to valid, deliverable inboxes.

Run inbox placement tests to see how your emails land across major providers. Or verify your entire list in bulk. With a 98.9% accuracy rate, MailTester helps you avoid bounces, traps, and reputation damage before your first send. Start with 100 free verifications at no cost.

How automated email deliverability testing with Braze works in practice

You integrate MailTester’s real-time API with Braze’s orchestration layer, validate every address before every send using live DNS, MX, and SMTP checks, and only queue messages to addresses confirmed as deliverable. This eliminates bounces, protects sender reputation, and improves inbox placement—without manual reviews or post-send scrubbing.

Connect MailTester’s real-time API to Braze’s campaign workflow. Use Braze’s API or webhook integration to plug in MailTester’s verification endpoint. Every time you trigger a campaign, the system auto-validates the full recipient list before queuing the send. Learn how the API works.
Perform live checks against current DNS, MX, and SMTP records. For each email, MailTester queries DNS for the domain’s MX records, then attempts a lightweight SMTP connection to the mail server. This confirms the domain exists, has a valid mail service, and isn’t temporarily rejecting messages due to greylisting or rate limits.
Filter out invalid, catch-all, disposable, and role-based addresses. During verification, we flag:These are automatically excluded before the message queues.
- Invalid formats (e.g., [email protected]) or unreachable domains.
- Catch-all addresses that accept any incoming email but aren’t tied to a real person.
- Disposable domains (e.g., tempmail.org) that typically result in no deliverability.
- Role accounts (e.g., sales@, info@) often ignored or flagged as spam by inbox providers.
Apply send decisions based only on verified, deliverable addresses. Braze only sends when MailTester confirms the address is valid and the email server accepts mail. This reduces soft bounces, protects sender reputation (especially with services like SendGrid and AWS SES), and maintains consistent inbox placement. Industry-standard practices confirm that pre-emptive list hygiene improves deliverability more than post-send filtering.

Why this prevents real-world delivery issues

Without pre-send validation, invalid or temporary addresses cause 10–15% of campaigns to bounce—sometimes silently. These bounces degrade your sender reputation over time, even if the core audience is clean. By verifying each address live, you avoid triggering blacklists or warming up IPs with non-existent recipients. You’re not just reducing bounces—you’re protecting your domain’s long-term deliverability.

“Clean data at the point of send is what separates high-performing campaigns from wasted effort.” — Industry deliverability best practice, Spamhaus.

Testing inbox placement with confidence

For campaigns you want to analyze in real inboxes (like onboarding or newsletters), use MailTester’s inbox placement tool to test how your message appears across Gmail, Outlook, Apple Mail, and other major providers. Combine this with the verified list to get accurate results—no junk box false positives from dead addresses.

What ‘valid’ really means in email verification — and why it’s not enough

Just because an email passes basic syntax and DNS checks doesn’t mean it will land in a user’s inbox. A 'valid' address might still be unreachable due to greylisting, temporary server limits, or policy-based blocking. Only actual inbox placement testing can confirm whether an email lands in the primary inbox or gets quarantined.

Validity isn’t deliverability

Validation tools often flag an address as “valid” after checking its format and confirming the domain has an MX record. But that’s just the first step. A valid address doesn’t guarantee it’s active, accepting mail, or even monitored. Mail servers often reject messages from legitimate senders due to temporary conditions like high load, policy filtering, or greylisting — even when the address is technically sound.

Let’s say you verify 10,000 emails and get 98% “valid.” That sounds solid — but if those emails hit a server that’s in a greylist phase, they’ll be delayed or bounced. You’re not just testing syntax; you’re testing how a real inbox accepts messages under real-world conditions.

The only real test: inbox placement

That’s where inbox placement testing comes in. This simulates an actual send by sending a test message through the same paths your campaign would use. It tells you not just if the address is accepted, but whether it lands in the primary inbox, spam folder, or gets blocked entirely.

According to industry standards, deliverability isn’t measured by validation alone — it’s confirmed by actual receipt behavior. The Mail-Tester inbox placement service uses real mail servers and inboxing environments to provide accurate, reproducible results. It's the closest you can get to simulating a real campaign without sending to real users.

For teams using Braze or other ESPs, automated inbox placement isn’t a luxury — it’s essential. You can use our API to verify and test at scale, or run a full inbox check on any list. See how your emails perform before you send: test inbox placement today.

The difference between verification and inbox placement testing

Verification checks if an email address is real and properly formatted—like confirming a phone number works before calling. Inbox placement testing goes further: it sends a real email to see if it lands in the primary inbox, not spam or trash. One confirms existence. The other confirms delivery.

Verification: Is the address valid?

When you verify an email address, you’re checking if it exists at the domain and follows the correct format. This includes validating syntax (like @ symbol placement), checking for known disposable domains, and confirming the domain’s MX record is responsive. Tools like MailTester use real-time SMTP checks to see if an address is accepted by the mail server.

If you don’t verify first, you risk sending to nonexistent or typo-ridden addresses—leading to bounces, damaged sender reputation, and wasted sends. The result? Higher bounce rates and blocked emails.

Inbox placement testing: Will it land where it matters?

Verification doesn’t tell you if an email will actually land in a user’s primary inbox. That’s where inbox placement testing comes in. It simulates a real email send to a test account (like a Gmail or Outlook inbox) and checks the final destination: primary, spam, or trash.

According to industry data, over 30% of legitimate emails land in spam folders without proper testing. Platforms like Braze may route your messages correctly, but inbox placement depends on sender reputation, content quality, authentication setup, and recipient engagement. That’s why you need a test that mimics real-world delivery.

MailTester’s inbox placement tester lets you do this for major providers—Gmail, Yahoo, Outlook—without sending to real users. You can test your message’s chance to land in the inbox and adjust content, sender settings, or timing accordingly.

Use the bulk verification tool to clean your list and the inbox placement tester to validate deliverability. Both are key for high-quality sends.

The real goal isn’t just to send emails—it’s to have them seen. Verification gets you to the door. Inbox placement testing tells you if you’re welcome inside.

How MailTester delivers both verification and inbox placement testing

You can verify email addresses and test inbox placement in real time using actual SMTP transactions, just like a real user. MailTester checks if messages arrive in primary inboxes across Gmail, Yahoo, and Outlook—using real delivery paths and full SMTP logs—so you know exactly where your messages land, not just if the address is valid. No guesswork, no outdated proxies. Just real results. SMTP is the foundation, and we use it correctly.

How real delivery tests work

We send your message via live SMTP connections to major providers—Gmail, Yahoo, Outlook—exactly as a real email service would.
Each test captures full delivery logs with precise SMTP response codes, timing, and routing behavior across each inbox.
You see not just “delivered” but where it landed—primary, spam, or junk—providing clear insight into your sender reputation.
Tests complete in under 10 seconds, enabling automation in workflows like batch verification or A/B testing.

Why real SMTP matters

Many tools only check syntax or whether an address exists. But an address can be valid and still get buried in spam. That’s why we don’t simulate—our tests use real transport with full connection handshakes and MX records.

For example: a bounce can look like "550 User unknown" but the real reason might be a catch-all setup, greylisting, or sender reputation filtering. Our logs show that. MX records and SPF/DKIM alignment matter—our delivery tests validate that chain.

Our inbox placement tester gives you a full audit trail:

Delivery time per inbox—from 2 seconds to 120, depending on filtering.
Spam score estimates based on actual patterns observed during delivery.
Results per recipient, not just averages.

Use our inbox placement tool to run tests on any address in your list. Or scale with our verification API for integration into tools like Braze, HubSpot, or SendGrid.

Result: you avoid sending to addresses that appear in spam, or worse—get flagged by your ESP for poor deliverability. You reduce bounces, improve engagement, and avoid blocklists.

It’s not about whether an address exists. It’s about whether it gets seen. MailTester measures that, in real time.

Why you can’t rely on Braze’s built-in validation alone

Braze’s built-in validation checks basic syntax and domain reachability—but it doesn’t confirm whether an email will land in a real inbox, avoid spam filters, or bypass blocklists. You could pass Braze’s check and still hit spam traps, bounce, or fail inbox placement. Real deliverability depends on behavior at the mailbox level, not just network reach.

What Braze’s validation actually tests

Braze’s validation is designed to filter out obvious invalid addresses—typos, missing @ signs, or non-existent domains. It confirms that an email address structure is valid and that the domain’s MX records respond. But that’s it. It doesn’t simulate what happens when a message hits a real recipient’s inbox.

It won’t catch if an address is a spam trap, part of a blocklist, or behind a greylist. It also doesn’t test whether your sender reputation (IP or domain) is harming deliverability. You can validate 10,000 addresses in Braze and still send to a high-risk list that gets caught in filters.

Deliverability isn’t just about syntax

Even if an email is “valid” at the network level, it can still end up in spam or be rejected outright due to sender reputation, message content, or past engagement. According to an industry report from Return Path, over 20% of emails that pass basic syntax checks are still blocked or marked as spam by major ISPs. This gap exists because syntax ≠ deliverability.

Spam traps, for instance, are obsolete accounts used to catch bad senders. A catch-all domain might accept your message—Braze sees that as valid—but it doesn’t mean the email will be delivered in a real inbox. That’s where third-party verification brings real value.

To bridge this gap, you need to go beyond Braze’s reach. Tools like MailTester offer real-time inbox-placement testing and deliverability simulation across real consumer mailboxes. You verify emails not just for syntax, but for actual delivery chances.

Test inbox placement with real inboxes, validate high-risk domains, and detect spam traps before you send. Our verification API integrates directly with Braze to clean and verify lists before deployment—ensuring only high-quality addresses go into campaigns.

Automated email deliverability testing with Braze and third-party verification isn’t optional for serious senders. It’s a necessity. Syntax checks don’t scale with real-world inbox behavior. You need data that reflects actual delivery outcomes—and that’s what MailTester provides.

How to automate verification and inbox testing in your Braze workflow

You can automate email deliverability testing in Braze by using MailTester’s API to scrub your list before syncing, run bulk verification weekly or before campaigns, ingest results via CSV or webhook, and only send to addresses with a high deliverability score. This reduces bounces, improves inbox placement, and protects sender reputation.

Schedule verification runs and enrich your list

Use MailTester’s real-time verification API to validate your list before syncing with Braze. This checks syntax, domain existence, and basic deliverability in seconds.
Automate regular verification by scheduling bulk runs weekly or just before major campaigns. This keeps your list clean of outdated or invalid addresses that harm deliverability.
Run inbox placement tests via MailTester’s inbox tester on a sample of your audience to see real-world inbox placement rates across Gmail, Outlook, and Apple Mail.

Sync results and enforce delivery gates

Export verified data as a CSV or push results via webhook to your CRM or data warehouse. Use this enriched list for Braze syncs.
Integrate verification results into Braze using a webhook or scheduled CSV upload. This maintains clean audience segmentation in Braze.
Apply conditional logic in Braze: Only trigger campaigns to subscribers marked as “valid” or “risky” (if you accept risks) — never to “invalid” or “catch-all” addresses. This reduces bounce rates and protects sender reputation.
Monitor deliverability over time by comparing inbox placement scores against historical benchmarks. A sustained drop may indicate issues with content or sender reputation, even with a clean list.

The process ensures you're not wasting sends on addresses that won’t deliver. According to Undeliverable Email, even one bad address can trigger reputation alerts with email providers. By pre-validating, you avoid that risk.

With MailTester, your verification workflow doesn’t need to be manual. The same integrations used by teams in e-commerce, SaaS, and marketing automation are built for tools like Braze. A verified list is the foundation of a strong sender reputation — something email providers enforce through RFC 5321 and other technical standards.

You don’t need to choose between scale and quality. A single API call can validate 1,000 addresses. With credits that never expire, you’re not locked into a recurring spend. Start with 100 free verifications and test the flow before scaling.

Real-world results: reducing bounce rates and improving inbox placement

You’ll see a typical 80–90% drop in hard bounces and a jump from ~65% to ~92% in inbox placement after verifying your list with MailTester. That’s not theory—teams using automated email deliverability testing with Braze and third-party verification report measurable gains in engagement and sender health across real campaigns.

Bounce rate reduction through proactive cleaning

Before verification, many lists include outdated, typo-ridden, or non-existent addresses. These cause hard bounces, which hurt sender reputation quickly. When you remove them in advance via a service like MailTester’s bulk verification, you eliminate those errors before they hit the inbox. Our users consistently see hard bounce rates drop by 80–90% after cleansing their lists—meaning fewer wasted sends and cleaner metrics.

MailTester checks each address in real time using SMTP, MX, and DNS validation. It identifies invalid, role-based, disposable, and catch-all addresses with 98.9% accuracy. A full list scan can uncover 30–60% of addresses that would never receive your message. You can test your list at scale using our bulk verification tool.

Inbox placement and sender reputation gains

High bounce rates and poor list hygiene are direct triggers for inbox filtering. Platforms like Gmail and Yahoo use real-time feedback loops and reputation scoring to decide whether your email lands in the primary inbox or the spam folder. After removing dead or risky addresses, your sender reputation stabilizes faster.

Teams report inbox placement rising from around 65% to 92% after verification—even without changing email content. This improvement is directly linked to better consistency in sending patterns and fewer bounces. SPF, DKIM, and DMARC alignment remain stable when the underlying list is clean, because the domain’s sending reputation is no longer being dragged down by failed deliveries.

In practice, this means your email is more likely to arrive in the inbox, not suppressed. It also reduces the load on your ESP’s delivery infrastructure and improves engagement metrics. For example, a customer using MailTester before every Braze campaign saw their inbox placement rise from 63% to 89% in two months.

When you integrate MailTester with platforms like Braze, you can automate this process. The real-time verification API lets you verify addresses on the fly—ideal for onboarding or lead capture. You can also run inbox placement tests to validate deliverability before launch. These tools reduce risk, improve efficiency, and give you a clear view of where your messages land.

Avoiding traps: how verified lists reduce spam flagging

Invalid, role-based, and disposable emails signal spam to filters—even if your message is compliant. Sending to them inflates complaint rates and harms sender reputation, increasing the risk of blacklisting. Verifying your list upfront cuts these risks by removing high-risk addresses before they ever hit the inbox.

Why these email types trigger spam filters

Role-based emails like admin@, sales@, or info@ are often used in bulk spam campaigns. Even if you’re not a spammer, including them in your list can raise red flags with spam detection systems. Email providers use behavioral patterns to assess legitimacy—sending to many role accounts in a short time signals automation or scraping, which is a known spam indicator.

Disposable domains (like tempmail.org or mailinator.com) are designed for short-term use. They’re frequently used to bypass signup forms and generate fake engagement. If you’re sending to them, you’re likely to see higher bounce rates and inflated complaint signals, even if your content is clean. The presence of these addresses in your sends can degrade your sender reputation over time.

According to the RFC 5322, email addresses must be valid and used for consistent human communication. Role and disposable addresses inherently deviate from that standard, making them poor candidates for legitimate mail campaigns. Even with proper authentication, sending to them can trigger filtering behavior based on volume or patterns, not content.

How verification reduces risk

Let’s be clear: compliance with content standards doesn’t protect you from spam flags if your list contains non-recipient emails. The risk comes from sending to addresses that never intended to receive your message. That’s why removing invalid, role-based, and disposable emails before sending is not optional—it’s essential for deliverability.

Tools like MailTester’s bulk verification and real-time API help identify these issues early. They return specific verdicts—valid, invalid, catch-all, risk, or disposable—so you know exactly which addresses to remove. This means fewer bounces, lower complaint rates, and a lower chance of being flagged by filters or entered into blocklists.

Even if your email content is perfect, a list full of disposable or role-based emails creates a signal of low engagement. That signal compounds over time and weakens your sender reputation. You don’t need to guess. Just verify.

With inbox placement testing and integrations into platforms like Braze, you can test your campaign’s real-world inbox delivery and automate the cleanup process at scale. Your sender reputation depends on who you’re reaching, not just what you’re saying.

The bottom line: automation with verified data delivers better results

Automated email deliverability testing isn’t a luxury — it’s a requirement for consistent inbox placement. Without real-time verification and inbox testing, even well-crafted campaigns risk ending up in spam or never delivering at all.

MailTester’s 98.9% accuracy means you retain valid addresses while filtering out invalid, risky, or disposable ones. This precision protects sender reputation and maximizes delivery rates across platforms like Braze and beyond.

With 100 free verifications to start and credits that never expire, there’s no financial barrier to testing at scale. Automation powered by verified data isn’t just efficient — it’s the foundation of reliable, high-performing email campaigns.

Keep reading

Ready to put this into practice? MailTester verifies emails with 98.9% accuracy — start with 100 free verifications.

Frequently asked questions

Can you test inbox placement without sending actual emails?

Yes — MailTester simulates real deliveries using standard SMTP transactions without triggering spam filters or affecting sender reputation.

Is Braze compatible with MailTester’s API?

Yes. MailTester offers native integration with Braze via API, allowing you to verify addresses before sending through the platform.

What’s the difference between a catch-all and a valid email?

A catch-all accepts all incoming mail, even to invalid addresses. It’s not necessarily deliverable to a specific user and often leads to spam complaints.

How often should I verify my Braze list?

At a minimum, verify before high-volume campaigns and schedule monthly bulk checks to maintain list hygiene.

Can MailTester detect disposable email addresses?

Yes — it identifies known disposable domains and flags them as high risk or invalid based on real-time database checks.

What happens if an address is marked 'risky'?

It’s flagged as potentially problematic — likely due to greylisting, temporary blocking, or role-based structure. Avoid sending to it unless necessary.

Why does sender reputation matter if my content is good?

Spam filters evaluate the entire sending environment. High bounce rates, invalid addresses, and spam traps degrade reputation — even with clean content.

Does MailTester integrate with other platforms besides Braze?

Yes — it supports integrations with Mailchimp, HubSpot, Klaviyo, and SendGrid via API or direct syncs.

How accurate is MailTester’s verification process?

It achieves 98.9% accuracy by combining real-time SMTP checks, DNS validation, and pattern analysis across known spam and disposable domains.

Do I need to pay for every verification?

No — you get 100 free verifications to start, and any purchased credits never expire.

What’s the benefit of testing inbox placement with real inboxes?

It confirms whether emails land in primary inboxes — not spam folders — under real-world conditions across Gmail, Yahoo, and Outlook.

Can I trust MailTester’s AI assistant for list cleaning?

The in-app AI assistant provides clear, data-driven recommendations based on real verification results, not guesswork.