Why are employees not receiving emails sent to customers and employees when no bounces are reported?

Summary

When employees don't receive emails sent to both customers and employees, despite the absence of bounce reports, the issue often stems from internal email handling processes after the message is accepted by the receiving server. This includes a multitude of potential causes: overly aggressive or misconfigured internal spam filters, especially within platforms like O365, that discard emails based on specific rules or configurations (e.g., blocking emails seemingly originating from the company but not sent via authorized servers); incorrect internal email server settings impacting routing; stringent DMARC policies rejecting emails sent 'on behalf of' the company without proper authorization; email client-specific filtering behaviors; greylisting mechanisms causing significant delivery delays; domain or IP addresses appearing on blocklists; SPF record misconfigurations; a poor sender reputation leading to filtering; and overly broad application of list-unsubscribe headers inadvertently blocking internal employee emails. The key is the email made it to the internal system which means there is an internal setting blocking emails.

Key findings

  • Internal Email Acceptance: The lack of bounce reports indicates the recipient mail server accepted the message initially.
  • Aggressive Internal Filtering: Overly strict or misconfigured internal spam filters and firewalls block emails.
  • EOP/O365 Filtering: Exchange Online Protection and O365 may filter messages based on configured anti-spam policies, quarantining or discarding emails.
  • Incorrect Server Config: Incorrect internal email server configurations hinder proper email routing.
  • DMARC Policy Restrictions: Strict DMARC policies might reject emails sent 'on behalf of' the company if unauthorized.
  • Blocklisting Issues: The domain or IP address might be on public blocklists.
  • SPF Record Errors: Improperly configured SPF records cause email rejections by receiving servers.
  • Poor Sender Reputation: A poor sender reputation can lead to internal security systems blocking or filtering emails.
  • Client-Specific Rules: Unique filtering rules within certain email clients affect internal recipients.
  • Greylisting Delays: Greylisting causes substantial delays for internally-bound emails originating from external sources.
  • Routing Misconfiguration: Internal routing misconfigurations prevent internal delivery from external domains.
  • List-Unsubscribe Issues: Overly aggressive list-unsubscribe headers inadvertently block internal emails.
  • Incorrect Email Addresses: Simple errors, like incorrect email addresses prevent delivery.

Key considerations

  • Contact Internal IT: Involve the internal IT department for investigation and resolution.
  • Audit Email Filters: Review internal email filtering and firewall rules for overly strict or misconfigured settings.
  • Review Email Security: Check the Domain and IP on blocklists to ensure emails get delivered.
  • SPF Record Validation: Validate SPF records and ensure all legitimate sending sources are included.
  • Employee Education: Educate employees to check their spam/junk folders and report any missing emails to IT.
  • Verify Email Addresses: Confirm the accuracy of employee email addresses in contact lists.
  • Review Unsubscribe Process: Assess how the unsubscribe is implemented.
  • DMARC configuration: Review that DMARC configuration is setup correctly.

What email marketers say
9Marketer opinions

Employees may not be receiving emails sent to both customers and employees, despite no bounce reports, due to a variety of internal factors. These include overly aggressive internal spam filters or firewalls blocking legitimate emails, incorrect internal email server configurations (particularly mail routing), strict DMARC policies rejecting 'on behalf of' emails, email client-specific filtering rules, greylisting causing delays, misconfigured internal routing rules, or even simple errors like incorrect email addresses. Essentially, internal systems may be treating these emails as unwanted, or misdirecting them.

Key opinions

  • Internal Filtering: Internal spam filters and firewalls might be too strict, blocking emails intended for employees.
  • Incorrect Configuration: Incorrect internal email server configurations, especially mail routing, can prevent delivery.
  • DMARC Policy: A strict DMARC policy may reject emails sent 'on behalf of' the company if not authorized.
  • Client-Specific Rules: Unique filtering rules in some email clients may affect internal recipients.
  • Greylisting Delays: Greylisting can cause significant delays for internally-bound emails originating from external sources.
  • Routing Issues: Internal routing misconfigurations can misdirect emails from external domains.
  • Incorrect Addresses: Simple errors like incorrect email addresses can cause delivery failures.

Key considerations

  • IT Audit: Conduct a thorough audit of internal email filtering and firewall rules.
  • Server Configuration Check: Verify internal email server configurations, especially mail routing settings.
  • DMARC Review: Review and adjust DMARC policies to ensure legitimate emails are not rejected.
  • Whitelisting: Whitelist the sending domain/IP address within the internal network.
  • Employee Education: Educate employees to check spam folders and report missing emails to IT.
  • Address Verification: Verify that employee email addresses are accurate within the client's contact lists.
Marketer view

Email marketer from Sender explains that the employee email could of been provided to the client wrong and emails have been sent to an incorrect email address that looks very similar to the users.

July 2021 - Sender
Marketer view

Email marketer from Gmass shares that a strict DMARC policy could be causing the issue if the email is sent 'on behalf of' the company domain but not through authorized servers. These emails might be rejected or silently dropped.

June 2024 - Gmass
Marketer view

Email marketer from Superuser suggests that the internal email routing is configured to have emails from an external domain be delivered to customer inboxes and any local users on the companies domain be blocked.

June 2024 - Superuser
Marketer view

Email marketer from Email on Acid explains incorrect internal server configurations can prevent some emails from reaching employees. Specifically, internal mail routing may not be properly set up to handle certain types of messages.

October 2022 - Email on Acid
Marketer view

Email marketer from Stackoverflow shares that Greylisting could be causing the emails to be heavily delayed to internal addresses as the email is coming from an external source.

June 2023 - Stackoverflow
Marketer view

Email marketer from Mailjet responds that emails can be marked as spam internally. Employees should check their spam folders, and internal IT should whitelist the sending domain/IP.

November 2024 - Mailjet
Marketer view

Email marketer from Neil Patel's Blog shares that internal firewalls or spam filters might be blocking emails sent to employees, even if external customers receive them. IT departments often have strict rules.

June 2022 - Neil Patel's Blog
Marketer view

Email marketer from Reddit shares that some companies have overly aggressive internal filters that block legitimate emails. Recommends contacting internal IT to investigate.

May 2024 - Reddit
Marketer view

Email marketer from Litmus answers that some email clients have unique filtering rules. Certain content or formatting may trigger these filters for internal recipients, even if external recipients receive the email fine.

December 2024 - Litmus

What the experts say
6Expert opinions

Emails failing to reach employees despite successful external delivery and no bounce reports often result from internal filtering mechanisms. Email systems accept the mail (hence no bounce), but internal spam filters, especially in systems like O365, might discard messages based on defined rules or misconfigurations, such as blocking emails using the company domain but not originating from its mail servers. Furthermore, overly aggressive list-unsubscribe headers can inadvertently block employees. Troubleshooting requires auditing internal filtering rules, contacting internal IT, and understanding that once a system accepts a message, its fate is beyond external visibility.

Key opinions

  • No Bounce, Acceptance Implies Internal Issue: The absence of bounce reports indicates the receiving mail server accepted the message, shifting the problem to internal handling.
  • Internal Filtering Rules: Companies, especially with systems like O365, use spam filters that domain admins configure to discard emails based on rules.
  • Misconfigured Filters: Possible misconfigurations include blocking emails using the company domain but not sent from its designated mail servers.
  • List-Unsubscribe Headers: Aggressive list-unsubscribe headers can inadvertently block internal employees, especially those who have unsubscribed from related company communications.

Key considerations

  • Contact Internal IT: Reach out to the internal IT department for assistance, as the issue lies within their systems.
  • Audit Internal Filters: Domain admins should audit internal email filtering rules for misconfigurations or overly aggressive settings.
  • Review List-Unsubscribe Practices: Examine the implementation of list-unsubscribe headers to prevent inadvertent blocking of internal employee emails.
  • Acknowledge System Responsibility: Understand that once a system accepts an email, troubleshooting delivery issues becomes the accepting system's responsibility.
Expert view

Expert from Word to the Wise explains that some companies use aggressive list-unsubscribe headers that can inadvertently block internal employees from receiving emails, especially if they've ever unsubscribed from anything related to the company. The header is blocking any emails sent to users of that email address so it is important to ensure that unsubscribes are limited to just the specific marketing list.

October 2021 - Word to the Wise
Expert view

Expert from Email Geeks shares that if the company uses spam filters like O365, the domain admin can instruct the filter to discard mail that triggers certain rules. Once the message is accepted, it is the accepting server’s responsibility, and internal IT should be contacted.

December 2021 - Email Geeks
Expert view

Expert from Email Geeks shares “Your system accepted the message and took responsibility for it. Once it’s been accepted, I can’t tell you what happened to it.

April 2024 - Email Geeks
Expert view

Expert from Email Geeks suggests a possible reason: “someone checkmarked the ‘throw away mail using our domain without coming from our servers’ box.” This setting will discard messages like the one described.

February 2023 - Email Geeks
Expert view

Expert from Email Geeks explains that quarantine won’t return a bounce because the mail is accepted by the receiving MX. Bounces only happen when the message is not accepted by the MX.

May 2023 - Email Geeks
Expert view

Expert from Spam Resource answers that employee filters may be misconfigured or too aggressive, resulting in legitimate emails being flagged as spam or blocked. Admins should audit internal filtering rules.

May 2022 - Spam Resource

What the documentation says
4Technical articles

When employees don't receive emails despite customers doing so and no bounces occurring, several potential causes exist related to email security and configuration. Microsoft's Exchange Online Protection (EOP) may be filtering messages based on anti-spam policies, leading to quarantine. Google Workspace highlights the possibility of the domain being on a blocklist, necessitating checks and email log analysis. Furthermore, an improperly configured SPF record, as detailed in RFC documentation, can cause rejection. Finally, a poor sender reputation, as indicated by Cisco Talos, can trigger internal security systems to block or filter emails.

Key findings

  • Anti-Spam Policies: Exchange Online Protection (EOP) filters messages using anti-spam policies, potentially quarantining legitimate emails.
  • Domain Blocklisting: The domain or IP could be listed on public blocklists, preventing delivery.
  • SPF Configuration: Improperly configured SPF records can cause receiving servers to reject emails.
  • Sender Reputation: A poor sender reputation can lead internal security systems to block or filter emails.

Key considerations

  • Quarantine Review: Admins should review quarantined messages within Exchange Online Protection (EOP) and adjust policies accordingly.
  • Blocklist Check: Check if the domain or IP is listed on any public blocklists.
  • SPF Record Verification: Ensure the SPF record is correctly configured to include all authorized sending sources.
  • Reputation Management: Monitor and improve the sender's IP and domain reputation to avoid triggering internal security systems.
  • Email Log Analysis: Check the email logs to see if the messages are being blocked or delayed.
Technical article

Documentation from Google Workspace Admin Help responds that the domain could be on a blocklist. Admins need to check if their domain or IP is listed on any public blocklists, which would prevent delivery. Also, check the email logs to see if the messages are being blocked or delayed.

September 2022 - Google Workspace Admin Help
Technical article

Email marketer from Cisco Talos shares that If the sending server's IP or domain has a poor reputation, internal security systems are more likely to block or filter those emails.

July 2021 - Cisco Talos
Technical article

Documentation from Microsoft Docs explains that Exchange Online Protection (EOP) might filter messages based on anti-spam policies. Admins can review quarantined messages and adjust policies.

August 2022 - Microsoft Docs
Technical article

Documentation from RFC details that an improperly configured SPF record can cause receiving mail servers to reject emails. Ensure the SPF record includes all authorized sending sources.

November 2022 - RFC