In this article we look at Why Are My Emails Being Rejected? Understanding Email Bounces and the Importance of Feedback Loops
Sending bulk emails is essential for many businesses and organisations, but the challenges of email deliverability (particularly rejected or bounced emails) can create headaches for senders.
These issues arise from factors ranging from authentication errors to spam complaints, and overcoming them requires understanding why emails bounce, the specific requirements for bulk senders, and the role of feedback loops (FBLs) in maintaining a healthy sending reputation.
Why Emails Bounce
When an email bounces, it means the email was not delivered to the recipient. Email bounces can be categorised as either "soft" or "hard.". Soft bounces are temporary issues, like a full inbox, whereas hard bounces are permanent, such as an invalid email address or domain.
However, even valid email addresses can result in bounces if senders do not meet essential email authentication and policy requirements:
- SPF Records: The Sender Policy Framework (SPF) validates that the sender's IP address/es are authorised to send emails on behalf of the domain in the "From" field. Without a valid SPF record, emails are often flagged as spam or worse rejected.
For outMail users looking to setup SPF for their domain please see the below KB articles :-
- What is a "SPF" record?
- How to create a Sender Policy Framework (SPF) Record to Authorise outMail Servers to send out your Email - DKIM Signatures: DomainKeys Identified Mail (DKIM) is an email authentication method that uses cryptographic signatures to verify that an email has not been tampered with in transit and that it comes from a legitimate source.
For outMail users looking to implement DKIM please see the below KB articles :-
- Why is DKIM signing of emails so important?
- How do I enable DKIM signing of emails through outMail?
- Why is DKIM signing using your own domain name more important than using a onmicrosoft.com DKIM key - DMARC Policies: Domain-based Message Authentication, Reporting, and Conformance (DMARC) builds on SPF and DKIM to align the "From" header domain with these records. Having a published DMARC policy is essential for improving deliverability.
For outMail users looking to implement a DMARC policy please see the below KB articles :-
- What is a "DMARC" record?
- What is DMARC, what's its purpose and why it is important?
A sender's failure to comply with these protocols often leads to bounced emails or delivery to spam folders. Ensuring these elements are correctly configured is the first step toward successful email delivery.
Requirements for Bulk Senders
Bulk senders face additional scrutiny from internet service providers (ISPs) and email service providers where the specific requirements must be met to ensure high deliverability and maintain sender reputation:
- Authenticate Your Email: As mentioned, implementing SPF, DKIM, and DMARC is required. For DMARC, it's advisable to use a relaxed alignment and include an “rua” tag to receive reports, helping you monitor alignment success and errors.
- Provide an Easy Unsubscribe Option: Offering recipients an easy way to unsubscribe (RFC 8058) reduces spam complaints and is now a requirement for Yahoo. This should be done both in the body of the email and with a email header field called "list-unsubscribe" (supporting either the one-click “Post” method or “mailto”). In the body of the message must be a visible unsubscribe link in the email body and not a stealthy link at the bottom of the email in a colour that nearly matches the background. See our article on List-Unsubscribe.
- Manage Spam Complaint Rates: High spam complaint rates damage sender reputation. Many ISPs set a spam rate threshold; staying below a 0.3% complaint rate can help avoid penalties and improve inbox placement.
- Implement Forward and Reverse DNS Records: Ensure that your sending IP has both forward and reverse DNS records configured, helping ISPs confirm the legitimacy of your domain. If you're using outMail for sending outbound emails then this is already configured.
- Adhere to Internet Standards: Bulk senders should comply with the SMTP protocol (RFC 5321) and email formatting standards (RFC 5322) to improve compatibility with recipient servers.
- Content is King: Remember the saying from all those SEO engineers you've spoken to, "Content is King". It's key to have a well written email to lower the chances of it triggering a spam filter. Most spam filters employ the use of realtime block lists (RBLs). If your email appears to be spam it will increase the RBL score and ultimately affect your sending reputation.
By meeting these requirements, senders can prevent their emails from being flagged or rejected by mail servers, particularly for large email campaigns.
What Are Email Feedback Loops?
An Email Feedback Loop (FBL) is a service provided by many ISPs that informs senders when a recipient marks their email as spam. Major providers like Yahoo, AOL, Hotmail, Microsoft and Gmail offer FBLs to help bulk senders track and manage spam complaints, ultimately helping to maintain sender reputation.
Feedback loops are particularly important because they give senders direct insights into how their audience responds to emails. When recipients frequently mark emails as spam, it indicates poor engagement or mismatched content, allowing senders to adjust their strategy accordingly.
The Importance of Feedback Loops in Bulk Email Marketing
Monitoring FBL reports is essential for email senders who want to maintain a positive sending reputation and deliverability:
- Early Detection of Complaints: FBL notifications allow senders to quickly remove from their lists those recipients who mark emails as spam. This minimises the number of complaints and helps prevent the sender’s domain or IP from being blocked or throttled by ISPs.
- Proactive Reputation Management: Regular monitoring of FBLs enables senders to identify trends in spam complaints, such as issues with a specific campaign or email type, allowing them to make timely changes.
- Improved Engagement: FBLs help senders ensure their messages reach engaged and interested subscribers by enabling the removal of disinterested or spam-reporting recipients. This reduces complaints, boosts sender reputation, and ensures the content reaches its target audience.
- Compliance with ISP Policies: Many email providers (e.g. Yahoo, Gmail, etc) have introduced stricter FBL-related policies, making it crucial for senders targeting these domains to utilise FBLs actively. ISPs now limit the proportion of spam complaints (typically 0.3%) allowed before they restrict or block the sender’s domain, making real-time complaint monitoring critical.
Best Practices for Feedback Loop Management
Here are some key strategies for effectively managing feedback loops:
- Regularly Monitor FBL Reports: Set up a dedicated email address for FBL reports and monitor it frequently to identify spam complaint trends.
- Remove Complainers Quickly: Promptly remove users who report your emails as spam to protect your sending reputation.
- Stay Policy-Compliant: Ensure that SPF, DKIM, and DMARC records are always up to date to maintain consistent delivery and sender reputation.
- Use Postmaster Tools: Many providers offer postmaster tools that allow you to monitor FBL data and stay proactive about managing complaints and reputation.
By leveraging FBLs and adhering to bulk-sending best practices, organisations can ensure successful email delivery, maintain a high sender reputation, and foster a more engaged subscriber base.
Setting up FBL
Please see below a list of KB articles for setting up RBL
About Prolateral
Prolateral Consulting is in business to put your organisation back in control of your own Information Technology, specialising in information and messaging security, inbound and outbound SMTP services, web hosting and DNS services.
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