When we doemail marketing, although the email has been sent, the recipient doesn't see it - this situation is more common than you think.Email deliverabilityis a key metric for measuring whether your email actually reaches the inbox, not simply "sent and done".Email deliverabilityand delivery rate are two different things: the delivery rate only looks at whether the email is received by the recipient's server, while the deliverability looks at whether it reaches the inbox. Many global enterprises have an email delivery rate of 99%, but the email open rate is less than 1%. The problem often lies inemail deliverability.

This guide will systematically explain how to improve ** email deliverability ** in five steps. USpeedo's email service users can directly follow the instructions.

What exactly is email deliverability? Why do businesses operating globally need to pay particular attention to it?

Email deliverability rate refers to the proportion of emails that successfully reach the inbox, excluding those that are blocked or end up in the junk folder. Gmail and Yahoo significantly tightened sender requirements between 2024 and 2025: Bulk senders (sending more than 5,000 emails per day) must configure SPF, DKIM, and DMARC, provide a one-click unsubscribe option, and keep the junk email complaint rate below 0.3%. Emails that do not meet these standards will be automatically sent to the junk folder by default.

For cross-border business, ** email deliverability ** poses greater challenges. The communication environments and user habits vary significantly across different markets, and email service providers in different countries have different strategies: Gmail and Outlook in the US are extremely sensitive to sender IP reputation, while European email services place more emphasis on DMARC policies. A set of incorrect ** email server ** configurations could cause all your verification codes and order notifications to sink to the bottom.

USpeedo's email service has deployed multiple nodes globally (Los Angeles, São Paulo, Hong Kong, etc.), with built-in whole-link authentication and automatic preheating mechanisms, helping you improve **email deliverability **from the architectural level.

Step 1: Domain Name Authentication (SPF + DKIM + DMARC)

Without valid identification, email service providers will not trust your emails. This is the foundation of improving email deliverability.

SPF( Sender Policy Framework)

SPF tells the recipient server which IP addresses are authorized to send emails on behalf of your domain. The configuration method is to add a TXT record in the domain DNS management panel:

v=spf1 include:spf.uspeedo.com ~all

If you are sending emails via USpeedo's SMTP or ** Email API **, simply add USpeedo's SPF record to your DNS. ** Email verification ** starts with ensuring SPF passes. Developers familiar with ** Email API ** know that there is no difference in authentication requirements between API and SMTP sending - SPF and DKIM are equally important for both methods.

DKIM( DomainKeys Identified Mail)

DKIM adds a digital signature to each of your emails, and the recipient's server uses your public key to verify whether the signature is valid.** This step of email verification ** ensures that the email content has not been tampered with during transmission.

DMARC( Domain-based Message Authentication, Reporting & Conformance)

DMARC tells the recipient server what to do if SPF or DKIM verification fails - accept, quarantine, or reject. It also sends reports to tell you who is sending emails in your name.

After adding a domain name in "Settings → Domains and Senders" of the USpeedo Console, the system will automatically generate these three DNS record values. Simply copy them to your DNS panel. After the domain name authentication is successful, ** email deliverability ** will have its first layer of protection. For more details about DNS records, you can refer to this 5-step plan for optimizing email deliverability .

Step 2: Sender Warm-up and Reputation Building

New domain names or new IPs have an initial reputation of zero with email service providers. If you send thousands of emails on the first day, the recipient server will directly throttle traffic.Email deliverability will be very low at this stage, which is a normal phenomenon.

The correct approach is ** progressive preheating **:

• Week 1: 200 - 500 per day

• Week 2: 1000-2000 emails per day

• Week 3-4: Gradually increase to normal sending volume

• Continuously monitor the bounce rate and complaint rate, keeping them below 2%

USpeedo's email service has a built-in automatic warm-up mechanism. If you are sending via email API, the system will automatically manage the sending rhythm. If you are configuring email server yourself, be sure to manually handle this step properly.

Step 3: Manage the quality of the recipient list

A low-quality recipient list is ** the number one killer of email deliverability **. Here are three things I believe every team should do:

Use Double Opt-in

After user registration, a confirmation email is sent, and only after clicking the confirmation link will the user be added to the official list. Although this may result in a 10-20% loss of registration conversion, it can eliminate spelling mistakes, role-based email addresses (info@, sales@), and auto-filled junk addresses.

Handle Bounced Emails Promptly

Hard Bounces (address does not exist) must be immediately removed from the list. Addresses with consecutive Soft Bounces (mailbox full, server busy) should also be treated as Hard Bounces after 3-5 occurrences.Email Delivery Rate is directly affected by the Bounce Rate - a Bounce Rate exceeding 5% will cause email service providers to question the quality of your list.

Group by Activity

Mark users who have opened emails within 30 days as active, initiate re-subscription confirmation for users who have not interacted for more than 90 days, and directly remove those who still do not respond. Maintaining list health is a key operation for long-term maintenance of email deliverability.

Step 4: Optimize Email Content and Sending Strategy

Content and sending strategy equally affect **email deliverability **. Here are a few principles I consider most important:

Content Level

• Avoid junk words: Although the weight of words like "free" and "guarantee" is decreasing, it is still recommended to use them with caution

• Maintain a reasonable ratio of text to images, and avoid having all images or all text

• Provide both HTML and plain text versions

• The sender name should use a brand name recognizable to users and should not be changed frequently

Sending Policy

• Maintain a stable sending rhythm to avoid sudden traffic spikes

• The sending frequency for active users can be doubled, while for dormant users, it can be halved. Regarding the strategy selection for batch sending, you can refer to this Traditional Mass Sending Method vs API Batch Sending

• Adjust the optimal sending time according to the time zone of the target market, and do not mass send to all regions at the same time

Step 5: Continuous Monitoring and Problem Troubleshooting

Email delivery rate is not an indicator that can be set and forgotten. You need to continuously monitor the following data:

On the "Analysis" page of the USpeedo Console, you can view the delivery rate, open rate, click-through rate, and bounce reasons in real time. It also supports configuring Webhooks to receive callbacks for sending status, facilitating integration into your own monitoring system. If you are using a self-built mail server, you can combine the mail API Webhook to do the same thing.

If you notice a sudden drop in the delivery rate, you can first check whether the DNS records have been accidentally modified, and then review the service provider's recent policy updates.

Frequently Asked Questions (FAQ)

What is the email delivery rate?

Email delivery rate refers to the proportion of emails that successfully reach the inbox out of the total number sent. It is different from the delivery rate, which only counts whether the email is received by the recipient's server, regardless of whether it ultimately ends up in the inbox or the junk folder.

What is the difference between the Email API and SMTP ?

The Email API is based on HTTP/REST and is suitable for development scenarios that require template management, webhooks, and bulk sending. SMTP is a standard protocol suitable for integration with Mail User Agents and self-built systems. USpeedo supports both methods.

How to prevent emails from being marked as junk email?

The key lies in three points: completing SPF/DKIM/DMARC domain authentication; controlling bounce and complaint rates; and using high-quality recipient lists. For specific operations, please refer to the five steps in this guide.

What are SPF and DKIM?

SPF declares which IPs are authorized to send emails on behalf of your domain. DKIM adds a digital signature to your emails to confirm their authenticity. Both are core components of email verification, and neither can be missing.

Start improving your email deliverability

Email deliverability rate optimization is not a one-time task but a continuous operational process. Starting from domain name authentication and systematically going through the steps of warm-up, list management, content optimization, and monitoring, your email deliverability rate can steadily improve. Every step in improving email deliverability rate is not complicated; the key lies in consistent implementation.

USpeedo's email service provides whole-link authentication for SPF/DKIM/DMARC, automatic warm-up, and real-time analysis features, with pay-as-you-go billing and zero monthly fees. New users will receive 10,000 free credits upon registration.

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