Email deliverability is the ability to land marketing messages in a subscriber’s primary inbox rather than the spam folder or being blocked entirely. It serves as a measurement of your sender reputation and how well your audience engages with your content. While related to email delivery, deliverability specifically focuses on inbox placement.
What is email deliverability?
Email deliverability is the likelihood of your campaigns reaching subscribers’ inboxes. It is influenced by internet service providers (ISPs), throttling by receiving servers, bounces, and spam filters. Unlike "delivery," which only confirms if a message reached the recipient's mail server, deliverability measures where that message sits after it arrives.
High deliverability ensures that your emails reach the primary inbox or tabbed inboxes, such as Google’s Promotions tab. It relies on a feedback loop of engagement: if people open and click your emails, your reputation improves, increasing your chances of reaching the inbox in the future.
Why email deliverability matters
Maintaining high deliverability is essential for the success of email marketing strategies. If messages land in the spam folder, they are likely to be ignored or deleted, making even the best content useless.
- Higher conversion potential: [39% of marketers using list segmentation see improved open rates] (Klaviyo), which leads to more sales opportunities.
- Reduced list churn: [28% of marketers see lower opt-out and unsubscribe rates] (Klaviyo) when deliverability and relevance are high.
- Increased revenue: [24% of practitioners report increased sales leads and greater revenue] (Klaviyo) following deliverability improvements.
- Reputation protection: Poor practices can cause an ISP to block your domain entirely, halting all communications.
How email deliverability works
When you send an email, a series of technical steps occur in the background to determine where the message lands.
- Composition: A message is created on an email service provider (ESP) platform.
- Transmission: The message is uploaded to a Simple Mail Transfer Protocol (SMTP), which moves it between servers.
- Discovery: The SMTP communicates with the Domain Name System (DNS) to find the recipient's server location.
- Verification: The receiving server checks the sender's IP reputation, blacklist status, and authentication records.
- Placement: The recipient’s SMTP decides if the email belongs in the inbox, the spam folder, or should be rejected.
Best practices
Following established technical and behavioral standards improves the chances of your email reaching the intended recipient.
- Authenticate your domain: Use SPF, DKIM, and DMARC records to prove your emails are legitimate. This tells mail servers you own the domain you are sending from.
- Warm up new infrastructure: If you move to a new IP or domain, start with low volumes and gradually increase them over 30 to 60 days. HubSpot users with a [dedicated IP go through an automated 40 day warm-up period] (HubSpot).
- Maintain list hygiene: Regularly remove inactive subscribers and invalid addresses. High bounce rates signal poor list management to ISPs.
- Use double opt-in: Require new subscribers to click a confirmation link in an email. This prevents fake or misspelled addresses from entering your database.
- Balance content types: Avoid sending image-only emails. Research indicates that [emails should contain at least 500 text characters to avoid spam filters] (Klaviyo).
- Monitor engagement: Track opens, clicks, and spam complaints to understand how your audience reacts. [Campaign Monitor maintains an overall delivery rate of 99%] (Campaign Monitor) by monitoring these trends.
- Implement BIMI: Set up Brand Indicators for Message Identification to show your brand logo in the inbox. This builds visual trust and increases brand recognition.
Common mistakes
Many marketers unintentionally trigger spam filters or damage their reputation through poor habits.
Mistake: Using all capital letters or excessive exclamation points in subject lines. Fix: Use standard sentence case. [85% of recipients prefer an all-lowercase subject line] (Klaviyo) over one in all caps.
Mistake: Sending from a free domain, such as @gmail.com or @yahoo.com, for bulk marketing. Fix: Use a branded sending domain that you own and have authenticated.
Mistake: Hiding the unsubscribe link to prevent people from leaving. Fix: Place a clear unsubscribe link at both the top and bottom of the email. If your [abuse rate hits even 0.05%, inbox providers may flag you as a "bad sender"] (Klaviyo).
Mistake: Using URL shorteners (like bit.ly) in message bodies. Fix: Use full, branded links, as many spam filters associate shorteners with malicious activity.
Mistake: Sending too many emails at once without ramping up. Fix: For new IP addresses, ramping to a [100k email volume can take 10 days, but mailbox providers may take 30 days] (Klaviyo) to decide on your initial reputation.
Email Deliverability vs. Email Delivery
| Metric | Goal | Key Factor | Result of Failure |
|---|---|---|---|
| Email Delivery | Reach the recipient's server. | Valid address, server uptime. | Hard or soft bounce. |
| Email Deliverability | Reach the recipient's inbox. | Sender reputation, engagement. | Message goes to spam. |
A campaign can have 100% delivery while having 0% deliverability if every message is routed to the spam folder.
FAQ
How long does it take to establish a sender reputation? When starting with a new domain or IP, the process typically takes 30 to 60 days of consistent sending. Mailbox providers often take about 30 days to make an initial decision on your reputation, though [validation of your reputation can take up to 120 days] (Klaviyo).
What is the difference between a hard bounce and a soft bounce? A hard bounce is a permanent error caused by an invalid or non-existent email address. A soft bounce is a temporary issue, such as a full inbox or a server that is momentarily down. High rates of either can damage your reputation.
How does "graymail" affect my deliverability? Graymail refers to emails that recipients technically opted into but never open. It sits unengaged in the inbox, which makes the sender look like a spammer to ISPs. Using features like graymail suppression helps exclude these contacts to improve overall engagement rates.
What are the bulk sender requirements for Gmail and Yahoo? Starting in February 2024, these providers enforced stricter rules for senders hitting certain volume thresholds. Specifically, [bulk senders who email 5,000 or more Gmail recipients per day] (Klaviyo) must use a branded sending domain and have a DMARC policy in place.
How can I test my deliverability before sending a campaign? You can send a test message to tools that analyze your headers, SPF records, and blacklist status. These tools generate a report showing potential issues before you send to your entire list.
