Email deliverability is critical to the success of your marketing campaigns. Even the most compelling content won’t drive results if it doesn’t reach your audience’s inbox. This guide outlines best practices to help ensure your emails are delivered successfully, especially when sending at scale.
Sender Reputation
Your domain and IP reputation are foundational to deliverability. ISPs (like Gmail, Yahoo, etc.) evaluate your sending history to determine whether to accept, reject, or filter your emails.
Private vs Shared IPs
Private IPs - A private (dedicated) IP is used exclusively by your organization.
- Benefits:
Full control over your sending reputation
Ideal for high-volume senders with consistent engagement
Easier to isolate and resolve deliverability issues - Considerations:
Requires careful warm-up and ongoing reputation management
Poor practices directly impact your reputation
Not ideal for clients who do not have consistent send volume year round
Shared IPs - A shared IP is used by multiple senders, Managed by Ascent360
- Benefits:
Reputation is distributed across multiple senders
Good for low-volume senders who can’t build reputation alone
Due to the shared send volume this is a good option for clients with seasonal volume spikes - Considerations:
Vulnerable to other senders’ poor practices
Less control over reputation and troubleshooting
Best Practices
- Use a dedicated sending domain (e.g., email.yourbrand.com)
- Warm up new domains and IPs gradually
- Monitor reputation using tools like Google Postmaster Tools, or SenderScore
Authentication Protocols
Proper authentication helps ISPs verify that your emails are legitimate and not spoofed. At Ascent360, we use SendGrid as our email delivery backend, which simplifies and automates much of the authentication process.
How SendGrid Manages Authentication
When your domain is configured for sending through Ascent360, we set up CNAME records in your DNS. These records delegate authentication to SendGrid, allowing it to automatically manage:
- SPF (Sender Policy Framework)
Verifies that SendGrid is authorized to send on behalf of your domain. - DKIM (DomainKeys Identified Mail)
Ensures email integrity and authenticity by signing messages with cryptographic keys. - DMARC (Domain-based Message Authentication, Reporting & Conformance)
Helps protect your domain from spoofing and phishing by enforcing alignment between SPF/DKIM and the “From” address.
Because these records are managed via CNAME delegation, SendGrid can rotate keys, update policies, and maintain best practices without requiring manual updates from your IT team.
Best Practices
- Ensure your DNS records are correctly configured during onboarding
- Use a branded sending domain (e.g., email.yourbrand.com)
- Periodically review your domain’s authentication status using tools like MXToolbox or Google Postmaster Tools
List Hygiene
Maintaining a clean and engaged email list is one of the most effective ways to improve deliverability and campaign performance. Today, sending to engaged individuals is more important than ever, as ISPs increasingly use engagement signals to determine inbox placement.
Why It Matters
- Reduces bounce rates and spam complaints
- Improves sender reputation and inbox placement
- Maximizes ROI by focusing on recipients who are most likely to act
Engagement-Based Filters to Use
To ensure you're only reaching active and interested customers, we recommend filtering your list using criteria such as:
- Opened an email in the last 30, 60, or 90 days
- Clicked a link in the last 30, 60, or 90 days
- Made a purchase or visited your website recently
- Subscribed or opted in within the last 6 months
These filters help you focus your efforts on recipients who are most likely to engage, improving deliverability and campaign effectiveness.
Best Practices
- Regularly suppress unengaged contacts from bulk sends
- Use re-engagement campaigns to win back inactive users
- Remove hard bounces and invalid addresses automatically (Ascent360 handles this automatically)
- Monitor list performance and adjust segmentation strategies as needed
- Consider an At Data email validation run > Link to At Data Documentation
Content Optimization
Your email content plays a major role in whether your message lands in the inbox or the spam folder. Spam filters evaluate everything from formatting and wording to code structure and sender behavior. Optimizing your content is essential for maintaining deliverability and driving engagement.
Key Elements of Optimized Content
- Subject Line Best Practices
- Keep it short and relevant (under 50 characters is ideal)
- Avoid spammy phrases like “Buy now,” “Free,” or “Act fast”
- Personalize when possible (e.g., “Bob, your pass is ready”)
- Body Content Guidelines
- Maintain a healthy text-to-image ratio (avoid image-only emails)
- Avoid excessive use of ALL CAPS, bold, or exclamation marks!!!
- Use clear, concise language that matches your brand tone
- Include a clear call to action (CTA) with a visible button or link
- Personalization & Dynamic Content
- Use merge tags to personalize with names, locations, or preferences
- Segment content based on behavior, interests, or purchase history
- Dynamic blocks can tailor messaging to different audience segments
- Mobile Optimization
- Use responsive design to ensure readability on all devices
- Keep paragraphs short and scannable
- Use large, tappable buttons for CTAs
- Compliance & Trust Signals
- Include a visible unsubscribe link and physical mailing address
- Avoid misleading headers or deceptive subject lines
- Use branding elements (logo, colors, sender name) to build trust
- Preheader Text
- Use preheader text to complement your subject line
- Avoid leaving it blank or repeating the subject line
- Testing & Tools
- Use platforms like Litmus or Email on Acid to preview your email across devices
- Run your email through Mail-Tester.com to check spam score
- Monitor engagement metrics to refine content over time
Sending Behavior
Your sending volume and frequency have a direct impact on how ISPs perceive your email traffic. Sudden changes in volume or erratic sending patterns can trigger spam filters or throttling.
Why it Matters
ISPs monitor your sending patterns to determine whether your emails are trustworthy. Consistent, predictable behavior builds credibility, while spikes or irregularities can raise red flags—even if your content and authentication are solid.
Ramp-Up Strategy: Start Slow, Build Trust
When launching a new domain or IP, it’s critical to gradually increase your sending volume over time. This process, known as warming up, allows ISPs to observe your behavior and engagement metrics before granting full inbox access.
Recommended Ramp-Up Guidelines:
- Start with small batches (e.g., 5,000–10,000 emails per day)
- Increase volume incrementally every few days
- Prioritize sending to your most engaged users first
- Monitor bounce rates, open rates, and spam complaints daily
- Ascent360 handles new IP warming automatically on your behalf
Maintain Consistent Patterns
Once warmed up, consistency is key. ISPs prefer senders who follow predictable schedules and maintain steady volume.
Avoid Risky Behaviors
- Don’t send to your entire list all at once after a long pause
- Avoid sending to unengaged or stale contacts during ramp-up
- Don’t switch IPs or domains frequently without proper warm-up
Best Practices:
- Send on regular days/times (e.g., weekly newsletters every Tuesday)
- Avoid large spikes in volume, especially after periods of inactivity
- Use segmentation to spread sends across time zones or engagement levels
Engagement Metrics
ISPs closely monitor how recipients interact with your emails to determine whether your messages are wanted—or should be filtered to spam. Engagement is one of the most powerful signals influencing inbox placement, especially with Gmail and Yahoo’s evolving standards.
Key Engagement Signals ISPs Track
- Open Rates: Indicates interest and relevance. Low open rates can signal poor targeting or weak subject lines.
- Click-Through Rates (CTR): Shows deeper engagement and content effectiveness.
- Spam Complaints: Even a small number of complaints can severely damage your sender reputation.
- Unsubscribes: A natural part of email marketing, but spikes may indicate poor targeting or frequency issues.
Why Engagement Matters More Than Ever
- High engagement improves inbox placement and sender reputation.
- Low engagement can lead to throttling, filtering, or outright blocking.
- ISPs now prioritize recipient behavior over sender volume or age.
Low engagement can lead to filtering or blocking. Use A/B testing and segmentation to improve performance.
Tools & Resources
- Google Postmaster Tools: Monitor Gmail-specific reputation, spam rates, and domain/IP performance
- MXToolbox: Check DNS records, authentication status, and blacklist presence
- Mail-Tester.com: Analyze your email’s spam score, authentication, and content quality
- At Data: Validates and enhances email addresses to improve list quality and reduce bounce rates
- SenderScore: Rates your IP reputation on a scale of 0–100 based on email sending behavior
Summary Checklist
✅ Send Consistently and Predictably
Stick to regular schedules and avoid sudden volume spikes, especially after inactivity.
✅ Segment by Engagement
Target users who opened or clicked in the last 30–90 days, or recently purchased or subscribed.
✅ Maintain List Hygiene
Regularly suppress unengaged contacts, remove bounces, and validate emails to reduce complaints.
✅ Use a Branded Sending Domain
Send from a subdomain like email.yourbrand.com to build brand recognition and reputation.
✅ Warm Up New IPs and Domains Gradually
Start with small sends to engaged users and scale volume over time to build trust with ISPs.
✅ Optimize Content for Deliverability
Avoid spammy language, use balanced formatting, and personalize subject lines and body content.
✅ Monitor Engagement Metrics
Track opens, clicks, complaints, and unsubscribes to refine targeting and improve inbox placement.
✅ Use Diagnostic Tools
Leverage Google Postmaster Tools, MXToolbox, and Mail-Tester.com to monitor reputation and spam risk.
