Why did my HTML email get delivered internally but not to external recipients?

Email marketer from Reddit explains that your domain's reputation is crucial for external deliverability. If your domain has a history of spam complaints, external servers are more likely to block your emails. Internal servers often have better trust for internal domains.

Marketer from Email Geeks explains that if emails were initially accepted but didn't reach inboxes, a spam filter might have removed them, or they might be in an IT-managed quarantine.

Marketer from Email Geeks identifies that the recipient's domain is managed by ProofPoint, indicating a general quarantine that recipients might not be able to see.

Email marketer from Litmus shares that even if an email renders correctly internally, different email clients (Gmail, Outlook, etc.) may interpret the HTML differently, which could lead to content being flagged as suspicious by external filters.

Email marketer from Mailjet explains that many companies whitelist their own domain internally, so emails sent within the company are more likely to be delivered. External servers don't have this whitelisting, leading to potential filtering.

Marketer from Email Geeks shares that HTML by itself should not cause a problem, but copying HTML code from a previously flagged spam message or using externally hosted fonts and images might cause issues. They also suggested checking if the recipients who didn't receive the email all use the same provider.

Email marketer from Sendinblue shares that external servers are more likely to check SPF, DKIM, and DMARC records to verify the sender's identity. If these records are not properly configured, external servers might flag the emails as suspicious.

Marketer from Email Geeks suggests identifying patterns among recipients and using a service like Email on Acid to flag potential issues. Coding mistakes can impact deliverability.

Marketer from Email Geeks outlines the following steps: 1. Send it to gmail and see what happens. 2. If there's an issue at gmail, strip the html so it's just text and send it. 3. Depending on that result, investigate from there.

Email marketer from SparkPost shares that engagement metrics such as opens, clicks, and replies affect email deliverability. Low engagement can signal to email providers that your emails are not relevant, leading to decreased placement.

Email marketer from Neil Patel's Blog explains that your IP address's reputation can significantly impact deliverability. If your IP address has been used for spam in the past, external servers might block emails from that IP, while internal servers are more likely to trust it.

Marketer from Email Geeks suggests checking the quarantine folder, which is different from the spam folder and often managed by the IT department. This folder contains emails deemed clearly bad and stopped before reaching spam.

Email marketer from StackOverflow explains that external email servers often have more aggressive spam filters that scan for specific words, phrases, or code patterns. These triggers might cause your email to be flagged as spam externally, while internal servers are more lenient.

Email marketer from HubSpot explains that using double opt-in and practicing good list hygiene are crucial for maintaining a healthy sender reputation. These practices help ensure that you are only sending emails to engaged recipients, which improves deliverability.

Email marketer from Gmass explains that using a dedicated IP address helps build a positive sending reputation. If you are on a shared IP address, your emails could be affected by the sending behavior of other users, leading to deliverability issues.

Email marketer from ActiveCampaign shares that feedback loops (FBLs) are mechanisms that allow email senders to receive notifications when recipients mark their emails as spam. Monitoring and acting on FBL data can help improve sender reputation and deliverability.

Expert from Email Geeks advises to first verify if recipients checked their spam folders and searched by subject line. He mentions that content-based issues rarely cause emails to completely vanish, so this initial check is crucial.

Expert from Email Geeks suggests having a recipient ask their IT team to investigate the issue, as they have the necessary information and a paid account with ProofPoint for assistance.

Expert from Word to the Wise explains that sender reputation can vary significantly between different ISPs and email providers. Internal email systems may have a pre-existing positive reputation for emails originating from within the organization, while external providers might not have any reputation data or might even have negative data if the domain or IP has been associated with spam in the past.

Expert from Email Geeks recommends using the ESP's suggested workflow, fixing any flagged errors, and sending a small campaign to an external email address (e.g., Gmail) for testing.

Expert from Spam Resource explains that internal networks often bypass standard DNS checks used by external mail servers. This can cause emails to be delivered internally even if there are DNS configuration issues (like missing SPF or DKIM records) that would cause external servers to reject the email.

Expert from Email Geeks advises sending a test email to a personal Gmail address. Corporate setups may whitelist their own domain, masking potential issues.

Expert from Email Geeks goes on to say sharing the 'Show Original' result can let people see if there's anything obviously borked and after due diligence, the nice folks at ProofPoint are often quite helpful.

Expert from Email Geeks suggests that the issue might be related to linking images via a local URL or a file link to an internal file server.

Documentation from Google Workspace Admin Help explains that Google Workspace allows administrators to set up custom email routing rules. These rules can affect how emails are delivered internally versus externally. Incorrect routing settings might cause external emails to be blocked or filtered.

Documentation from RFC 7231 explains that the Content-Type header and MIME types in HTML emails must be correctly formatted. External servers might be stricter about enforcing these standards, and if there are errors, emails may be rejected or filtered.

Documentation from Cisco explains that their SenderBase Reputation system tracks the reputation of IP addresses and domains based on various factors, including spam volume, blacklisting, and user complaints. A poor SenderBase reputation can lead to emails being blocked or filtered by Cisco's email security appliances.

Documentation from Microsoft explains that Exchange Online Protection (EOP) has different filtering policies for internal and external emails. EOP might apply stricter rules to external emails to protect against spam and phishing, leading to different delivery outcomes.