How to Improve Transactional Email Deliverability (and Stay Out of the Spam Folder)

Transactional emails are the backbone of digital communication—password resets, order confirmations, shipping updates, and security alerts all fall into this category. These messages are time-sensitive and expected, which makes their deliverability absolutely critical. If your transactional email lands in spam or fails to arrive altogether, it’s not just inconvenient—it erodes user trust.

Let’s walk through how you can improve your transactional email deliverability and ensure your emails reliably hit the inbox.

What Is Email Deliverability?

Email deliverability is the likelihood that your email reaches the recipient’s inbox rather than their spam or junk folder. Even with a functioning SMTP server or email API, there are many reasons why your message might get filtered out by mailbox providers like Gmail, Outlook, or Yahoo.

Improving deliverability means optimizing both your infrastructure and your email practices to signal to ISPs that you’re a trustworthy sender.

1. Set Up Email Authentication (SPF, DKIM, and DMARC)

The foundation of good deliverability starts with properly configured domain authentication.

• SPF verifies that the IP address sending the email is allowed to send on behalf of your domain.
  
• DKIM signs your email with a private key to prove it hasn’t been altered in transit.
  
• DMARC builds on SPF and DKIM to tell mailbox providers how to handle unauthenticated emails and gives you visibility through reports.
  

Without these, your emails are more likely to be rejected or filtered as spam.
Learn more: SPF, DKIM, and DMARC for Transactional Email

2. Use a Reputable Email Sending Platform

Whether you send via SMTP or API, your provider’s reputation matters. Choose a platform with:

• Strong IP reputation management
  
• Pre-warmed IP pools or IP warmup support
  
• Built-in compliance with email best practices
  

MailChannels, for example, offers automatic IP reputation management, which reduces your chances of being blacklisted.

3. Separate Transactional and Marketing Emails

Sending all your emails from the same IP or domain is risky. If your marketing emails cause spam complaints, it can negatively affect your transactional delivery.

Use a separate subdomain and IP for transactional messages to protect their deliverability.

For example:
transactional.yourdomain.com for transactional
marketing.yourdomain.com for newsletters and promos

4. Avoid Spam Trigger Words and Poor HTML

Even though transactional emails are not promotional, poorly formatted messages can still look suspicious. Follow these rules:

• Avoid all caps or excessive exclamation marks in subject lines
  
• Use clean HTML with inline CSS only
  
• Include a plain-text version of your email alongside the HTML version
  
• Don’t embed large images or external scripts
  

5. Monitor Engagement and Bounce Metrics

Mailbox providers consider recipient behavior when deciding inbox placement. If your messages have high bounce or complaint rates, your reputation will take a hit.

• Hard bounces should be immediately removed from your list
  
• Monitor open and click rates to track engagement
  
• Watch spam complaint rates through feedback loops
  

Not monitoring bounce and complaint rates? You’re flying blind.

6. Respect Sending Cadence and Volume

Inconsistent sending patterns—like bursts of high volume followed by silence—can trigger filtering. Aim to send emails consistently and warm up new IPs gradually.

If you’re switching providers or sending from a new IP, start with lower volume and gradually increase over several days or weeks.

Read: IP Warmup for Transactional Email Using MailChannels

7. Use Clear and Consistent Sender Identity

Mailbox providers want to see consistent branding in your emails. That includes:

• A recognizable “From” name and email address
  
• Accurate reply-to addresses
  
• Properly configured reverse DNS (PTR) records
  
• Matching HELO hostnames
  

This helps build trust and reduce the chances of being flagged as suspicious or spoofed.

8. Test Inbox Placement Regularly

Use inbox placement testing tools or seed lists to verify that your emails are hitting the inbox and not landing in spam folders. Don’t just rely on open rates—they can be misleading due to privacy protections like Apple Mail Privacy.

9. Keep Your Lists Clean—Yes, Even for Transactional Email

While transactional emails are typically sent to opted-in users, inactive or invalid addresses can still end up on your list due to:

• Typos during sign-up
  
• Abandoned accounts
  
• Fake email addresses from bots
  

Use double opt-in where appropriate and validate email addresses at sign-up or before sending.

Final Thoughts

Deliverability isn’t just about sending email, it’s about ensuring email is received. With the right infrastructure, authentication, and sending habits, your transactional messages will consistently land where they belong: in the inbox.

Need a deliverability-first approach to transactional email?
Try MailChannels Transactional Email and get built-in protections, domain authentication, and inbox-friendly infrastructure from day one.