If you’ve built an app that sends signup confirmations, password resets, or transactional notifications — and users tell you “it landed in my spam” — you’re not alone.
Even with great code and legit intentions, your app’s emails can silently fail. Let’s break down why this happens — and how to fix it with some simple (but often overlooked) steps.
This post is for indie hackers, SaaS founders, and devs shipping products that send email.
Problem: Your Emails Aren’t Trusted
Mail services like Gmail, Outlook, or Yahoo are on high alert. They don’t just ask “Is this email spam?” — they ask “Can I trust this sender at all?”
To answer that, they look at:
- Who sent it (domain reputation)
- Whether the domain allows that sender (SPF/DKIM)
- Whether someone is spoofing you (DMARC)
- Whether you're on any spam blacklists
If these aren’t correctly set, even legit apps get treated like spam.
Fix: Authenticate Your Domain
Think of email authentication as giving your domain an ID badge — proving to receiving mail servers that your app is allowed to send on your behalf.
There are three records that matter:
1. SPF (Sender Policy Framework)
“Which servers are allowed to send email from my domain?”
You publish a DNS TXT record listing the IPs or services (e.g. SendGrid, Postmark, Amazon SES) you use to send mail.
Example SPF record:
v=spf1 include:sendgrid.net ~all
This tells mail servers, “Only SendGrid can send for me. Anyone else? Treat as suspicious.”
2. DKIM (DomainKeys Identified Mail)
“Can we verify the email content hasn’t been altered, and it’s really from this domain?”
DKIM adds a cryptographic signature to your emails. Mail servers check your public key (in your DNS records) to verify the signature.
✅ If it matches, it’s authentic.
🚨 If it fails, the email may be forged or tampered.
3. DMARC (Domain-based Message Authentication, Reporting & Conformance)
“What should happen if SPF or DKIM fails?”
With DMARC, you set a policy:
-
none: just monitor and report -
quarantine: send failed mail to spam -
reject: block failed mail completely
Example DMARC record:
v=DMARC1; p=quarantine; rua=mailto:dmarc-reports@yourdomain.com
You also get reports that show who’s sending mail from your domain — helping you catch abuse.
🛠️ “Is this domain ready to send email?” - Test It All
By now you might be wondering:
“Okay, but how do I know if my domain has these things set up correctly?”
That was the exact problem I kept running into while building my own projects. My team would launch something, email about it — and then... users wouldn’t see them. Debugging meant jumping between five tools, parsing DNS errors, and reading outdated docs.
So I built a free tool to help developers, founders, and technical folks like us quickly answer the question:
“Is this domain ready to send email?”
You just plug in a domain. In a few seconds, you get a clear overview:
✅ SPF: present, valid?
✅ DKIM: detected, correctly signed?
✅ DMARC: set, policy in place?
🚫 DNS issues: misconfigurations or missing records?
🚫 Blacklists: is this domain showing up anywhere?
No signups, no noise — just a quick, honest check so you can move forward (or fix what's broken). Feel free to try it out at MXAuditor.com — I’d love to hear if it helps your flow.
Bonus Tips
- Use a reputable email provider (Postmark, SendGrid, SES, Mailgun, etc.)
- Warm up your domain (don’t blast 1,000 emails on day one)
- Use a custom return-path domain when possible
- Avoid spammy phrases (especially in subject lines)
- Authenticate your email links (HTTPS, branded if possible)
TL;DR
If you’re building apps that send email — you need to care about email authentication.
✅ SPF: “Only these senders are allowed”
✅ DKIM: “Yes, this email came from me and wasn’t changed”
✅ DMARC: “If SPF/DKIM fail, here’s what to do”
Use MXAuditor to check if your domain is set up correctly — so your app emails land in inboxes, not the void.
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