How to Improve Email Deliverability

What is email deliverability

Email deliverability is the measure showing what percentage of your emails successfully reach the recipient's inbox instead of the spam folder or being rejected entirely. Even with perfect email content, if the message ends up in spam, the recipient probably never sees it. The average deliverability rate is about 85 percent, meaning out of every 100 sent emails, 15 never reach the inbox. For a business that depends on email communication, this can mean lost opportunities and revenue.

Deliverability depends on many factors including your domain and IP reputation, technical server configuration, email content, recipient behavior, and compliance with anti-spam laws. Improving deliverability is a continuous process that requires attention to all of these aspects. Learn more about setting up email on your domain because weakness in one area can undo efforts in all others.

Warming up domain and IP address

Why warm-up is necessary

When you start sending emails from a new domain or new IP address, email providers like Gmail, Outlook, and Yahoo have no data about your reputation. If you immediately start sending thousands of emails, this looks like spammer behavior and your emails will be blocked or flagged as spam. Warm-up is the process of gradually increasing the number of emails you send over 2 to 4 weeks until you build a positive reputation.

Warm-up plan

Start day one with 20 to 50 emails per day, sending them to users you know will open and respond to your email, like colleagues, partners, or your most active subscribers. Each day increase volume by 30 to 50 percent. By the end of the first week you should be sending about 200 emails per day. During the second week increase to 1,000, the third to 5,000, and the fourth to full volume. Track open rates and spam complaints throughout the process. If open rate drops below 20 percent or spam complaints appear, slow down.

Email authentication

SPF (Sender Policy Framework)

SPF is a DNS record that defines which servers are authorized to send emails on behalf of your domain. Without SPF, anyone can send an email that looks like it comes from your domain, a technique known as email spoofing. The SPF record is added as a TXT record in your domain's DNS and contains a list of IP addresses and servers authorized to send. Use the include mechanism to add servers of email services like Google Workspace or Microsoft 365, and end the record with -all for strict rejection of unauthorized senders or ~all for soft rejection.

DKIM (DomainKeys Identified Mail)

DKIM adds a digital signature to every email proving the message truly comes from your domain and wasn't modified in transit. When you send an email, your server adds a cryptographic signature to the message header using a private key. The recipient's server checks the signature using the public key published in your domain's DNS. If the signature matches, the email is authentic. The DKIM key should be at least 2,048 bits long for adequate security and should be rotated every 6 to 12 months.

DMARC (Domain-based Message Authentication)

DMARC ties SPF and DKIM into a unified framework and defines what the recipient's server should do with an email that fails authentication. DMARC policies are none which only monitors without action, quarantine which sends unauthenticated emails to spam, and reject which fully rejects unauthenticated emails. Start with the none policy to track who sends emails on behalf of your domain without the risk of blocking legitimate messages. Once you confirm all legitimate sources are configured with SPF and DKIM, move to quarantine then to reject.

Email content optimization

Avoiding spam trigger words

Spam filters analyze email content looking for words and phrases typical of spam. Words like free, urgent, guaranteed, last chance, click now, make money, and similar raise the message's spam score. This doesn't mean you should never use these words, but use them sparingly and in natural context. Excessive use of capital letters, exclamation marks, and special characters also raises a red flag with spam filters.

HTML vs text balance

An email containing only images without text is a common spam sign because spammers use images to bypass text-based spam filters. Maintain a text-to-image ratio of at least 60 to 40 in favor of text. Every image should have alt text. Avoid oversized images because many email clients don't load images automatically. Email HTML code should be clean, without unnecessary styles and JavaScript which is blocked in all modern email clients anyway. Inline CSS is the only reliable way to style emails.

Personalization and relevance

Personalized emails have a 26 percent higher open rate than generic messages. Use the recipient's name in the subject and body of the email, segment the list by interests and behavior, and send relevant content that matches subscriber expectations. Emails recipients regularly open, read, and respond to improve your reputation with email providers, which directly affects deliverability of all future messages.

Reputation management

Tracking metrics

Key metrics for tracking deliverability are deliverability rate which should be above 95 percent, open rate which depends on industry but should generally be above 20 percent, spam complaint rate which must be below 0.1 percent, bounce rate which should be below 2 percent, and unsubscribe rate. Use tools like Google Postmaster Tools which provides insight into your domain's reputation with Gmail users, Microsoft SNDS for Outlook, and Yahoo Feedback Loop for tracking spam complaints from Yahoo users.

List hygiene

Regularly clean the email list of inactive subscribers, invalid addresses, and spam traps. Invalid addresses that generate bounces negatively affect your reputation. Spam traps are email addresses placed by email providers or anti-spam organizations to identify senders sending unwanted mail. Implement a double opt-in process where the subscriber must confirm subscription by clicking a link in an email, which reduces the risk of invalid addresses and spam complaints. Automatically remove addresses that generate hard bounces.

Blacklist monitoring

What blacklists are

Blacklists are databases of IP addresses and domains determined to send spam. Email servers check these lists before accepting email and reject or flag messages from blacklisted senders. The most well-known blacklists are Spamhaus, Barracuda, SORBS, and Spamcop. Getting on a blacklist can drastically reduce deliverability because your emails get rejected by a large number of servers.

Monitoring and removal

Regularly check whether your IP address and domain are on any blacklist using tools like MXToolbox or MultiRBL which simultaneously check dozens of lists. If you find yourself on a list, each blacklist has a removal process that usually requires you to identify and fix the problem that led to listing. Some lists automatically remove IP addresses after a period without spam activity while others require a manual request. Prevention is better than cure - follow best practices for email sending so you never end up on a list. On BeoHosting email servers we have full SPF, DKIM, and DMARC authentication configured and we actively monitor blacklists so your emails reliably reach the recipient's inbox.

Conclusion

Improving email deliverability requires a systematic approach covering technical configuration with SPF, DKIM, and DMARC authentication, careful warming up of new domains and IP addresses, email content optimization, regular subscriber list cleaning, and continuous reputation and blacklist monitoring. The investment in deliverability pays back many times over because every email that lands in the inbox instead of spam is an opportunity for communication, sales, or building a customer relationship.