Best Practices to Avoid Spam Emails: Ensuring Inbox Delivery

Getting your emails delivered to the inbox, and not the spam folder, is crucial for effective communication. Spam filters are constantly evolving, making it essential to adopt and maintain best practices for email sending. This article provides a detailed guide on improving your email deliverability, focusing on authentication, content optimization, list management, and technical configurations, offering actionable steps to help you reach your audience effectively.

Table of Contents

• Email Authentication: SPF, DKIM, and DMARC
• Content Optimization: Avoiding Spam Trigger Words and Poor Formatting
• List Management: Building and Maintaining a Healthy Email List
• Technical Configurations: IP Reputation and Reverse DNS

Email Authentication: SPF, DKIM, and DMARC

Email authentication is the cornerstone of preventing your emails from being flagged as spam. It verifies that you are who you say you are, building trust with email providers and improving your sender reputation. Implementing SPF, DKIM, and DMARC is crucial for establishing this trust and ensuring your messages reach the intended recipients’ inboxes.

Understanding SPF (Sender Policy Framework)

SPF is a DNS record that specifies which mail servers are authorized to send emails on behalf of your domain. When a receiving mail server gets an email, it checks the SPF record of the sending domain to verify if the email originated from an authorized server. If it doesn’t match, the email is more likely to be marked as spam.

Example: Let’s say your domain is `example.com` and you send emails through Google Workspace. Here’s how to configure your SPF record:

v=spf1 include:_spf.google.com ~all

Explanation:

• v=spf1: Specifies the SPF version.
• include:_spf.google.com: Includes Google’s SPF records, allowing Google Workspace to send emails on your behalf.
• ~all: Indicates a softfail. If an email doesn’t match the SPF record, it should be accepted but marked with a warning (less strict than `-all`).

Important Considerations:

• Avoid using ‘+all’: This is highly discouraged as it allows anyone to send emails on behalf of your domain, negating the purpose of SPF.
• Regularly update your SPF record: If you start using a new email service provider (ESP), update your SPF record to include their servers.
• Test your SPF record: Use online SPF record checkers to ensure it’s valid and correctly configured. A simple Google search for “SPF record checker” will provide multiple options.

Implementing DKIM (DomainKeys Identified Mail)

DKIM adds a digital signature to your emails, which is then verified by the receiving mail server using a public key published in your DNS records. This signature confirms that the email was sent by the claimed sender and hasn’t been tampered with during transit.

Example: Configuring DKIM in Google Workspace:

• Generate a DKIM key: In your Google Workspace admin console, navigate to Apps > Google Workspace > Gmail > Authenticate email. Generate a DKIM key (e.g., 2048-bit).
• Add the DKIM record to your DNS: Google will provide a TXT record. It will look something like this:

google._domainkey.example.com.  TXT  "v=DKIM1; k=rsa; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAyCgY4..."

Explanation:

• google._domainkey.example.com.: The DKIM record name (selector). The “google” part is often customizable.
• TXT: Indicates a TXT record.
• "v=DKIM1; k=rsa; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAyCgY4...": The DKIM record value. v=DKIM1 specifies the DKIM version, k=rsa indicates the key type (RSA), and p= contains the public key.

Important Considerations:

• Key Length: Use a 2048-bit key for stronger security.
• Rotation: Regularly rotate your DKIM keys for enhanced security. This involves generating a new key pair and updating the DNS record.
• Testing: After adding the DKIM record, use email testing tools to verify that DKIM is properly configured and your emails are being signed.

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

DMARC builds upon SPF and DKIM by defining what receiving mail servers should do with emails that fail authentication checks. It allows you to specify a policy (e.g., reject, quarantine) and receive reports about authentication failures, providing valuable insights into potential spoofing attempts.

Example: Setting up a DMARC record:

_dmarc.example.com.  TXT  "v=DMARC1; p=none; rua=mailto:dmarc-reports@example.com; ruf=mailto:dmarc-forensic@example.com; adkim=r; aspf=r; rf=afrf1:mailru"

Explanation:

• _dmarc.example.com.: The DMARC record name.
• TXT: Indicates a TXT record.
• "v=DMARC1; p=none; rua=mailto:dmarc-reports@example.com; ruf=mailto:dmarc-forensic@example.com; adkim=r; aspf=r; rf=afrf1:mailru": The DMARC record value.
  • v=DMARC1: Specifies the DMARC version.
  • p=none: Sets the policy to “none,” meaning no action is taken on failing emails. This is recommended initially for monitoring. Other options are `quarantine` (emails are moved to spam) and `reject` (emails are rejected).
  • rua=mailto:dmarc-reports@example.com: Specifies the email address to receive aggregate reports (daily summaries of authentication results).
  • ruf=mailto:dmarc-forensic@example.com: Specifies the email address to receive forensic reports (detailed reports about individual failing emails).
  • adkim=r: DKIM alignment mode, set to relaxed.
  • aspf=r: SPF alignment mode, set to relaxed.
  • rf=afrf1:mailru: Reporting format, specifies the format of the reports, default being AFRF. Mailru requires specific format for DMARC reports, so this is tailored for that purpose.

Important Considerations:

• Start with “p=none”: Begin by setting your DMARC policy to “none” to monitor your email authentication results without impacting delivery. Analyze the reports to identify any legitimate emails that are failing authentication.
• Gradually increase policy: After monitoring for a while, gradually increase the policy to “quarantine” and then “reject” as you become more confident in your authentication setup.
• Analyze reports: Regularly analyze the DMARC reports to identify and address any authentication issues. This will help prevent legitimate emails from being blocked.
• RUA and RUF: It’s important to set up both RUA (Aggregate Reports) and RUF (Forensic Reports), although some providers might not support RUF. RUA provides summary data and RUF provides details that are essential for diagnosis.

By implementing SPF, DKIM, and DMARC correctly, you significantly enhance your email authentication, improving your sender reputation and increasing the likelihood of your emails reaching the inbox.

Content Optimization: Avoiding Spam Trigger Words and Poor Formatting

The content of your emails plays a critical role in whether they land in the inbox or the spam folder. Spam filters analyze email content for suspicious words, phrases, and formatting patterns. Optimizing your email content to avoid these triggers is essential for maintaining a good sender reputation and ensuring your message gets through.

Avoiding Spam Trigger Words and Phrases

Certain words and phrases are commonly associated with spam and can trigger filters. While the specific list varies across providers, some common culprits include:

• Financial: “Free money,” “Make money fast,” “Guaranteed income,” “Investment opportunity”
• Promotional: “Click here,” “Buy now,” “Limited time offer,” “Special promotion”
• Medical: “Miracle cure,” “Weight loss,” “Health breakthrough”
• Sensational: “Urgent,” “Important,” “Act now,” “You’ve been selected”
• Salesy: “Best price,” “Lowest rates,” “Amazing deal,” “Don’t miss out!”

Example: Let’s compare two subject lines:

• Bad: “URGENT: Claim your FREE money now!” (Contains multiple spam trigger words and excessive capitalization)
• Good: “Important Update: Your account information” (Clear, concise, and avoids trigger words)

Important Considerations:

• Use synonyms: Instead of “free,” try “complimentary” or “no cost.” Instead of “buy now,” try “learn more” or “view details.”
• Context matters: The same word can be harmless in one context and spammy in another. For example, “investment” is fine in a legitimate financial report but suspicious in an unsolicited email promising quick riches.
• Proofread carefully: Typos and grammatical errors are common in spam emails and can raise red flags.

Optimizing Email Formatting

Poorly formatted emails are another common spam indicator. Spam filters look for patterns that are often associated with unsolicited messages, such as excessive use of images, large font sizes, and unusual colors.

Example: Consider these formatting issues:

• Excessive capitalization: WRITING IN ALL CAPS is a surefire way to trigger spam filters.
• Large fonts and bright colors: Using excessively large fonts and jarring colors can make your email look unprofessional and spammy.
• Excessive use of images: Sending an email that is primarily composed of images with little or no text can also trigger spam filters.

Best Practices for Email Formatting:

• Maintain a good text-to-image ratio: Ensure that your email contains more text than images. A good rule of thumb is at least 60% text and 40% images.
• Use appropriate font sizes and colors: Use standard font sizes (12-14 points) and avoid overly bright or contrasting colors.
• Use proper HTML formatting: Ensure your HTML code is clean and valid. Avoid using outdated or deprecated HTML tags.
• Optimize images: Compress your images to reduce file size, which improves loading times and prevents your email from being too large. Use appropriate alt text for images in case they don’t load.

Example HTML code for an image with alt text:

<img src="https://www.example.com/image.jpg" alt="Description of the image" width="600" height="400">

Explanation:

• src: Specifies the URL of the image.
• alt: Provides alternative text for the image, which is displayed if the image cannot be loaded and is important for accessibility.
• width and height: Specifies the width and height of the image in pixels. It’s best to explicitly set these values.

Testing Your Email Content

Before sending out a large email campaign, it’s crucial to test your email content to identify any potential spam triggers. Several online tools can help you analyze your email content and provide recommendations for improvement.

Example: Using a spam testing tool:

• Mail-Tester: Mail-Tester provides a score for your email based on various factors, including SPF, DKIM, DMARC, and content analysis. It also identifies any spam trigger words or formatting issues. Mail-tester.com
• GlockApps: GlockApps tests your email deliverability across different email providers and spam filters. It shows you whether your email lands in the inbox, spam folder, or is blocked.

By carefully optimizing your email content and testing it before sending, you can significantly reduce the chances of your emails being flagged as spam and improve your overall deliverability.

List Management: Building and Maintaining a Healthy Email List

The quality of your email list is a major determinant of your sender reputation and deliverability. A healthy email list consists of engaged subscribers who have explicitly opted in to receive your emails. Poor list management practices, such as sending emails to purchased lists or neglecting inactive subscribers, can lead to high bounce rates, spam complaints, and a damaged sender reputation.

Building an Opt-In Email List

The best way to build a healthy email list is to acquire subscribers through opt-in methods. This means that subscribers actively consent to receive your emails. There are two main types of opt-in:

• Single Opt-In: Subscribers are added to your list immediately after submitting their email address.
• Double Opt-In: Subscribers are sent a confirmation email that they must click to verify their subscription. This is the recommended method as it ensures that the email address is valid and that the subscriber genuinely wants to receive your emails.

Example: Implementing double opt-in:

• Subscription Form: Create a signup form on your website where visitors can enter their email address.
• Confirmation Email: After submitting the form, send a confirmation email with a clear call to action (e.g., “Confirm your subscription”).
• Thank You Page: Once the subscriber clicks the confirmation link, redirect them to a thank you page and add them to your email list.

Important Considerations:

• Clearly State Your Intent: Let subscribers know what type of emails they will be receiving and how often.
• Provide a Clear Unsubscribe Link: Make it easy for subscribers to unsubscribe from your list. This is not only a legal requirement but also helps to prevent spam complaints.
• Avoid Pre-Checked Boxes: Never pre-check the opt-in box in your signup form. Subscribers should actively choose to subscribe.

Segmenting Your Email List

Segmenting your email list involves dividing your subscribers into smaller groups based on specific criteria, such as demographics, interests, or purchase history. This allows you to send more targeted and relevant emails, which improves engagement and reduces the likelihood of spam complaints.

Example: Segmenting based on purchase history:

• Customers who purchased product A: Send them information about related products or special offers.
• Customers who purchased product B: Send them a different set of recommendations based on their purchase history.
• Customers who haven’t purchased anything in 6 months: Send them a re-engagement campaign to encourage them to make another purchase.

Benefits of Segmentation:

• Higher Open Rates: Targeted emails are more likely to be opened and read.
• Higher Click-Through Rates: Relevant content is more likely to generate clicks.
• Lower Unsubscribe Rates: Subscribers are less likely to unsubscribe from lists that provide value.
• Improved Deliverability: Engaged subscribers signal to email providers that your emails are welcome.

Cleaning Your Email List

Regularly cleaning your email list is essential for maintaining a healthy sender reputation. This involves removing inactive subscribers, bounced email addresses, and spam traps.

Example: Implementing a list cleaning process:

• Identify Inactive Subscribers: Identify subscribers who haven’t opened or clicked on your emails in a specific period (e.g., 6 months).
• Send Re-Engagement Campaign: Send a re-engagement campaign to these subscribers, offering them an incentive to stay subscribed.
• Remove Unengaged Subscribers: Remove subscribers who don’t respond to the re-engagement campaign.
• Handle Bounces: Immediately remove hard bounces (permanent delivery failures) from your list. Monitor soft bounces (temporary delivery failures) and remove them after a certain number of attempts.

Important Considerations:

• Frequency: Clean your email list regularly, at least every 3-6 months.
• Tools: Use hubspot-email-marketing-tactics-to-boost-roi/" class="internal-link" title="3 Hubspot Email Marketing Tactics to Boost ROI">email marketing platforms or third-party services to automate the list cleaning process.
• Spam Traps: Be aware of spam traps, which are email addresses used to identify spammers. Avoid purchasing email lists, as they often contain spam traps.

By focusing on building an opt-in email list, segmenting your subscribers, and regularly cleaning your list, you can significantly improve your sender reputation and ensure your emails reach the inbox.

Technical Configurations: IP Reputation and Reverse DNS

Beyond content and list management, several technical configurations play a crucial role in email deliverability. Your IP address’s reputation and proper DNS settings significantly impact how email providers view your messages. Optimizing these elements is essential for maintaining a trustworthy sender identity and ensuring your emails reach their destination.

Understanding IP Reputation

Your IP address’s reputation is a score based on your sending behavior, used by email providers to assess the trustworthiness of your emails. Factors influencing IP reputation include:

• Sending Volume: Sudden spikes in sending volume can negatively impact your reputation. Gradually increase your sending volume over time (warm-up).
• Bounce Rate: High bounce rates indicate poor list quality and can harm your reputation.
• Spam Complaints: A high rate of spam complaints signals that your emails are unwanted and will damage your reputation.
• Spam Trap Hits: Sending emails to spam traps is a major red flag and can severely damage your IP reputation.
• Authentication: Correctly configured SPF, DKIM, and DMARC are crucial for establishing a positive IP reputation.

Example: Warming up an IP address: When starting with a new IP address, it’s essential to gradually increase your sending volume to build a positive reputation. A typical warm-up schedule might look like this:

Day	Emails Sent
Day 1	500
Day 2	1,000
Day 3	2,000
Day 4	4,000
Day 5	8,000

Important Considerations:

• Monitor Your IP Reputation: Use online tools to track your IP reputation. Some reputable providers include SenderScore.org and Talos Intelligence.
• Use a Dedicated IP Address: For higher sending volumes, consider using a dedicated IP address to isolate your reputation from other senders.
• Avoid Shared IP Address Issues: If using shared IP addresses (common with smaller ESPs), ensure the ESP is diligently managing the IP reputation.

Configuring Reverse DNS (rDNS)

Reverse DNS (rDNS) is a DNS record that maps an IP address back to a domain name. It helps email providers verify that the IP address sending emails is associated with the domain it claims to represent. A properly configured rDNS record can significantly improve your email deliverability.

Example: Setting up rDNS:

• Contact Your ISP or Hosting Provider: You typically need to contact your ISP or hosting provider to set up rDNS, as they control the reverse DNS zone for your IP address.
• Provide Your Domain Name: Provide the fully qualified domain name (FQDN) that you want to associate with your IP address. This should be a domain that you own and use for sending emails.
• Verify the Configuration: Use online tools to verify that your rDNS record is correctly configured.

Example command to check rDNS using `dig`:

dig -x your_ip_address

Expected Output:

; <<>> DiG 9.18.18 <<>> -x your_ip_address
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 51139
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;your_ip_address.  IN  PTR

;; ANSWER SECTION:
your_ip_address. 3600 IN PTR mail.example.com.

;; Query time: 0 msec
;; SERVER: 192.168.1.1#53(192.168.1.1) (local)
;; WHEN: Tue Oct 24 10:30:00 2023
;; MSG SIZE  rcvd: 79

Explanation:

• your_ip_address: Replace this with your actual IP address.
• ANSWER SECTION: This section shows the result of the reverse DNS lookup. If the rDNS is configured correctly, it will show your domain name (e.g., `mail.example.com`).

Important Considerations:

• Match Your Sending Domain: The domain name in your rDNS record should match the domain you use in your “From” address.
• Consistency: Ensure consistency between your rDNS record, SPF record, and DKIM signature.
• PTR Record: The output contains a PTR (Pointer) record which maps the IP to the domain name.

By carefully managing your IP reputation and configuring reverse DNS correctly, you can significantly improve your email deliverability and ensure your messages reach the inbox.