The reliability of email delivery is paramount. Yet, a common and perplexing issue often arises: an email is shown as sent but never reaches the recipient’s inbox. This problem leads to confusion and frustration and can have serious implications, such as missed opportunities, delays in projects, or even damage to professional relationships.

Understanding the underlying causes of this email deliverability issue is essential for anyone relying on email as a primary means of communication. The reasons are multifaceted and often interconnected, from spam filters and full inboxes to server configurations and IP issues. This article delves into the common causes of email deliverability problems, offering actionable insights and best practices to ensure that your important communications reach their intended destination. 

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Why is My Email Shown as Sent but Not Received by Recipient?

Email deliverability is a complex issue that often leaves senders puzzled when an email is shown as sent but not received by the recipient. This phenomenon can be attributed to a multitude of factors, each of which requires careful consideration

Common Causes of Email Deliverability Issues

Emails sent out but not being received are a concern that affects both individuals and businesses. Understanding the root causes of this problem is the first step towards finding a solution. Here are some of the most common reasons why emails may not be reaching mail inboxes:

Spam Filters

Email service providers have advanced spam filtering algorithms designed to protect users from unwanted emails. These filters utilize complex algorithms to analyze email content, sender reputation, user feedback, and other factors. However, they can sometimes mistakenly mark legitimate emails as spam.

Important emails, such as business communications, newsletters, or personal messages, may end up in the spam folder, going unnoticed by the recipient. This can lead to missed opportunities, misunderstandings, or even financial loss.

Marketing emails or newsletters that contain certain trigger words, links to blacklisted domains, or patterns resembling known spam might be classified as spam. Even emails from reputable sources can be flagged if they share characteristics with known spam content.

Actionable Insights

• Check Spam Folder Regularly: Encourage recipients to regularly check their spam folders and mark legitimate emails as “Not Spam.” This helps in training Gmail’s algorithms.

• Whitelist Trusted Senders: If certain senders are consistently marked as spam, recipients can add them to their contacts or whitelist their email addresses. This ensures that future emails from these senders are delivered to the inbox.

• Avoid Common Spam Triggers: Senders should be aware of common spam triggers, such as using excessive capitalization, spammy phrases, overuse of exclamation marks, or including suspicious links. Crafting emails that avoid these triggers can improve deliverability.

Full Inbox

Gmail accounts have a storage limit, which includes not only emails but also files in Google Drive and photos in Google Photos. When this limit is reached, new emails cannot be received, and the account effectively becomes locked from receiving further communications.

Emails sent to a full inbox are bounced back to the sender with a failure notification, leading to a breakdown in communication. This can result in missed opportunities, delays in projects, or even damage to professional relationships.

A user who has not cleared old emails, attachments, or stored large files in Google Drive may face this issue. For instance, a business professional awaiting an important contract or proposal may not receive it if their Gmail storage is full, causing unnecessary delays and confusion.

Actionable Insights

• Regularly Monitor Storage: Users should regularly check their Gmail storage usage, which includes emails, attachments, Google Drive files, and Google Photos. This proactive approach helps in avoiding unexpected surprises.

• Clean Up Unnecessary Emails and Files: Encourage users to delete or archive old emails, especially those with large attachments. Utilizing tools like Google’s storage management can assist in identifying files that can be safely removed.

• Utilize Google One for Additional Storage: If storage needs consistently exceed the free limit, users may consider subscribing to Google One for additional storage space. This ensures uninterrupted email communication.

Blocked Senders

Gmail allows users to block specific email addresses or domains, providing a way to filter out unwanted communications. Emails from blocked senders are automatically discarded, never reaching the inbox. While this feature is useful for managing spam or unwanted contacts, it can sometimes lead to accidental blocking of legitimate senders.

Important emails from friends, colleagues, or business partners may go unnoticed if they have been blocked. This can lead to misunderstandings, missed opportunities, or even strained relationships.

Imagine blocking an email address in a moment of annoyance, perhaps due to an unwanted marketing email, and then forgetting to unblock it later. If that email address later becomes associated with a legitimate contact, such as a new colleague or client, their emails will not be received, leading to confusion and potential loss of trust.

Actionable Insights

• Review Blocked Senders List Regularly: Encourage users to periodically review their blocked senders list in their emails. This helps in identifying and unblocking any legitimate email addresses that may have been accidentally blocked.

• Implement Whitelisting: If you’re a business, consider implementing whitelisting procedures. Asking recipients to add your email address to their whitelist ensures that your emails are not accidentally blocked

Email Configuration Issues

Incorrect SMTP (Simple Mail Transfer Protocol) settings, DNS (Domain Name System) configurations, or other technical misconfigurations can prevent emails from being delivered. These settings are crucial for properly routing and delivering emails, and any mistakes in their configuration can lead to emails being blocked or filtered.

Even perfectly legitimate emails may not reach the recipient due to these technical barriers. This can lead to confusion, delays in communication, and potential loss of trust or business opportunities.

An email sent from a misconfigured email client or server, such as using an unknown domain name in the “From” field or failing SPF (Sender Policy Framework) records checks, can lead to legitimate emails being blocked or moved to the Junk folder.

Actionable Insights

• Verify Email Addresses: Ensure that the “From” email address exists on the company server and is not failing SPF Records checks. There are many email checker tools that can verify if an e-mail address exists on the server. An invalid e- mail address will receive an error message and a bounce back. Always use email verification to improve deliverability.

• Use Valid Domains: To prevent emails from being blocked, add a valid/existing domain in the “From” field. Avoid using domains that are known to cause issues, such as *@yourportalname.csod.com or [email protected].

• Configure SPF Records: Be sure to add SPF records to your email domain. In the SPF records, include only the IPs for your Data Center, as this helps in authenticating the email source.

• Work with the recipient to determine if mail servers are in fact being blocked by the recipient’s mail server.

Gmail Filters and Rules

Users can set up custom filters and rules on their Gmail account to organize their emails. These filters can automatically sort emails into specific folders, label them, or even delete them based on certain criteria. While this feature enhances email management, sometimes these rules may inadvertently divert emails away from the inbox, leading to confusion and missed communications.

Emails may be moved to unexpected folders, making them hard to find or even leading to accidental deletion. Important communications might be overlooked, leading to delays, misunderstandings, or loss of opportunities.

A common example of this issue is a filter that moves all emails with attachments to a specific folder. If this rule is too broadly applied, it can cause important attached documents to be missed, such as contracts, invoices, or project files.

Actionable Insights

• Review and Test Filters Regularly: Encourage users to periodically review and test their Gmail filters and rules. This helps in identifying any rules that may be diverting important emails to unexpected locations.

• Provide Clear Guidelines: Offer clear guidelines on how to set up and manage filters and rules in Gmail. This includes understanding the criteria that trigger specific actions and how to test rules to ensure they work as intended.

Authentication Failures

Authentication failures occur when an email lacks proper authentication mechanisms, such as Sender Policy Framework (SPF) and DomainKeys Identified Mail (DKIM). These technologies are used to verify the legitimacy of the email’s source, ensuring that it has not been altered or forged. Like many email providers, Gmail relies on these authentication methods to filter out potential spam or malicious emails. Lack of proper authentication can lead email service providers to mistrust the source of the email.

Emails from unauthenticated sources may be marked as spam or rejected outright by Gmail. This can lead to legitimate emails being overlooked or lost, causing confusion, delays, and potential damage to reputation.

A common example of this issue is emails sent from a domain without proper SPF records. Without these records, Gmail may not be able to verify the email’s source, leading to it being classified as spam or even rejected.

Actionable Insights

• Implement SPF and DKIM: Ensure and test SPF and DKIM records are properly configured for your domain. These records help an e-mail provider like Gmail verify the authenticity of your emails.

• Monitor Authentication Failures: Regularly monitor for authentication failures and take prompt action to correct any issues. This includes reviewing bounce notifications and logs that may indicate authentication problems.

Server & IP Issues

Problems with the transmitting IP, server blacklisting, or reverse DNS lookup can hinder email delivery. Professional servers and proper SMTP settings can mitigate these issues. Understanding the intricacies of these technical aspects is crucial for ensuring seamless email communication.

Transmitting IP Issues

The IP address used to send emails plays a vital role in email deliverability. If an IP address is associated with spam or malicious activities, it may be blacklisted by email providers, causing emails sent from that IP to be blocked or filtered. You can use our blacklist tester to see if you are.

Actionable Insights

• Monitor IP Reputation: Regularly check the reputation of the IP addresses used for sending emails. Tools like Sender Score can provide insights into how email providers view a particular IP.

• Use Dedicated IPs for Critical Communications: Consider using dedicated IP addresses for important business communications. This ensures that the reputation of the IP is controlled solely by your organization’s email practices.