Why Your Emails Go to Spam: 18 Reasons and How to Fix Each One
Most deliverability problems come down to a small set of fixable mistakes. Let's discuss 18 mistakes, what they are, why they happen, and how to fix each one.
Akash Bhadange • 30 Dec, 2025 • [how to guide](/content/blog/topics/how-to-guide "how-to-guide"/index.html)
You already know which emails are the problem.
The welcome email that 30% of new users never see. The password reset buried under Gmail's Promotions tab. The product update your customers swear they never received.
Most frustrating part of email is, these problems are very hard to find and figure out. You might think all of this is happening because of the email content. But many times it's a technical or behavioral mistake that spam filters have been trained to catch and most of them are completely fixable once you know what to look for.
I run AutoSend, an email service that helps you send transactional and marketing emails. I have seen many of our customers making these mistakes constantly.
A customer with 100k sending volume reached out to us because none of their campaigns were working out. I check their setup and spot it immediately: they're sending from noreply@, and they just blasted 17,000 emails from a three-week-old domain.
These aren't edge cases. They're the most common reasons emails land in spam.
Quick Self-Diagnosis
Before reading the full guide, check these first. If any of these are true, fix them before anything else:
- SPF record missing or misconfigured
- DKIM not enabled on your sending domain
- DMARC policy not set
- Sending from noreply@ or no-reply@
- Domain is less than 60 days old and you're sending volume
- No unsubscribe link in marketing emails
- Complaint rate above 0.1%
- Bounce rate above 3%
If you checked two or more of these, start there. Those are your biggest deliverability killers.
Critical Mistakes (Fix These First)
These will get you blacklisted or blocked fast. If you're making any of these, everything else is secondary.
1. Missing Email Authentication (SPF, DKIM, DMARC)
Why it causes spam: Inbox providers treat unauthenticated emails as impersonation attempts, with no way to verify you are who you claim to be.
How to fix it: Set up all three in your DNS records. Verify they're working with a tool like MXToolbox or mail-tester.com. If you're sending through AutoSend, we verify your DKIM during domain setup. You'll see a green check in your dashboard once it's confirmed.
For a full walkthrough: How SPF, DKIM, and DMARC Work Together
2. Sending from noreply@ or no-reply@
You might want to send OTPs and transactional email via no-reply email ids as this is a standard practice. But, if your domain is new and you do not have much sending reputation, try to avoid it.
How to fix it: Use a real address. hello@, support@, team@, or your own name. If you need to suppress replies for a specific email type, use a filter on the inbox instead of a dead-address sender.
3. Deleting Contacts and Re-Uploading to Bypass Unsubscribes
This one is a BIG NO! This violates CAN-SPAM and GDPR.
How to fix it: Never delete suppression lists. They're not a list of failures. They're a record of people who have the legal right not to hear from you.
4. Missing Unsubscribe Link or Postal Address
How to fix it: Every marketing email needs a one-click unsubscribe and your business address in the footer.
High-Impact Mistakes
These won't get you blacklisted overnight, but they cause a steady reputation decline. If you're seeing a gradual drop in deliverability or inconsistent inbox placement, one of these is likely the cause.
5. Blasting Volume from a Brand New Domain
How to fix it: Warm up your domain over 2–4 weeks. Start with 50–100 emails per day to your most engaged contacts. Gradually increase volume.
Full guide: How to Warm Up a New Email Domain
6. Cold Emailing from a New Domain
How to fix it: Before you start any cold outreach, spend at least two weeks warming your domain with transactional or engaged-subscriber email.
7. Using URL Shorteners ( bit.ly, tinyurl, etc.)
How to fix it: Use full destination URLs. If you need click tracking, use a custom domain short link that's authenticated and associated with your brand.
8. Purchased or Scraped Email Lists
How to fix it: Only email people who explicitly opted in. No shortcuts here.
9. Mismatched From and Reply-To Domains
How to fix it: Keep both addresses on the same authenticated domain.
For Developers Sending Transactional Email via API
10. Not Handling Bounces via Webhook
How to fix it: Set up webhook listeners for bounce and complaint events. Hard bounces should be suppressed immediately.
11. Sending All Email Types from the Same Domain
How to fix it: Use a subdomain for transactional email.
12. Not Monitoring Complaint Rate
How to fix it: Set up Google Postmaster Tools for your sending domain.
13. Ignoring Soft Bounces
How to fix it: Track soft bounce patterns.
Medium-Impact Mistakes
14. Poor Text-to-Image Ratio
How to fix it: Keep a 60/40 or 70/30 text-to-image ratio. Always include a plain text version of every email.
15. Too Many Links
How to fix it: Keep it to 3–5 links maximum. Every link should have a clear purpose.
16. Spammy Subject Lines
How to fix it: Write subject lines that accurately describe what's inside.
17. Generic Greetings
How to fix it: Use first name personalization.
18. Excessive Capitalization and Exclamation Marks
How to fix it: Write like a human having a normal conversation.
Closing note
You don't need to fix all 18 at once. Work through them in order of severity:
- Critical first: Authentication (SPF, DKIM, DMARC), list hygiene, legal compliance
- Then high-impact: Domain warmup, bounce handling, list quality
- Then developer-specific: Webhook setup, subdomain separation, monitoring
- Medium last: Formatting, subject lines, content patterns
The bottom line for emails is, be genuine with your users and you will get more value from everyone. Email is a 40-year-old technology, so in whatever way you try to hack it, it will catch you and that will impact your business directly.