Why are login verification emails not being received despite showing as delivered in logs?
Summary
What email marketers say15Marketer opinions
Email marketer from Email Geeks suggests doing an inbox placement test and a deep dive on metrics for the specific mail stream. If the content is different, it might be the issue, so check for insecure elements (HTTP instead of HTTPS) and ensure images are losslessly compressed.
Email marketer from Email on Acid advises ensuring your sending IP or domain isn't on any email blocklists, which can cause delivery issues despite logs showing successful sending.
Email marketer from Litmus reports authentication issues (SPF, DKIM, DMARC) can cause email to be marked as spam even if delivered to the server. Suggests verifying authentication setup.
Email marketer from GMass writes that IP reputation can affect whether emails reach the inbox or spam. Low IP reputation might cause recipient servers to filter or delay emails despite successful initial delivery.
Email marketer from Email Geeks clarifies that checking MX records aims to identify which spam filtering systems are catching the messages to look for commonalities.
Email marketer from Email Geeks explains that the message might be delivered to the receiving mail server but quarantined, especially in corporate mail delivery. Checking the MX records for the custom domains can reveal which mail service or spam filter is in use (e.g., Google Workspace, Office 365, Proofpoint, or Mimecast).
Email marketer from Reddit explains that the receiver may have specific custom filters set up that are catching login verification emails. These would override global spam settings.
Email marketer from SendGrid discusses that recipient servers may have specific policies that affect delivery. Even with successful delivery to the server, the server might quarantine or delay the email based on reputation, content, or sender behavior. Monitoring your sender reputation is essential.
Email marketer from Reddit's r/emailmarketing comments that the user may have accidentally unsubscribed or been added to a suppression list. Suggests checking suppression lists to ensure the user isn't blocked.
Email marketer from Email Geeks suggests that the first place to look is the MTA's send log to confirm if the message was sent and accepted.
Email marketer from GlockApps emphasizes that engaging content and proper list management can help prevent emails from going to spam folders even if they are delivered. Lack of engagement can lead to filtering.
Email marketer from Mailchimp explains that obtaining explicit permission from recipients to send emails is crucial for deliverability. Sending emails to people who haven't opted-in can increase the likelihood of them being marked as spam, leading to filtering issues despite successful delivery.
Email marketer from Stack Overflow posts that greylisting (temporary rejection of emails from unknown senders) could delay email delivery. The recipient server initially rejects the email and expects the sender to retry. If the sending server doesn't retry or if the retry is delayed, the email might not be received promptly.
Email marketer from EmailGeek forum states that there may be delayed filtering rules - some rules aren't applied immediately. If there were recent changes it may be that the message was accepted prior to a filtering rule change.
Email marketer from Mailjet highlights that even if technically delivered, content can trigger spam filters on the recipient's end. Using certain keywords, excessive links, or poor HTML formatting can cause emails to be filtered despite proper authentication. Review content for common spam triggers.
What the experts say5Expert opinions
Expert from Spam Resource explains that DNS issues can cause authentication failures (SPF, DKIM, DMARC) that might not be immediately obvious but lead to deliverability problems. Suggests carefully reviewing DNS records.
Expert from Spam Resource discusses Seedlisting to test inbox placement with real accounts before sending. This proactive approach can help identify if emails are landing in spam folders despite showing as delivered.
Expert from Email Geeks mentions that ideally, delivery details should include a three-digit number, a peer IP address, and a timestamp.
Expert from Email Geeks suggests looking for delivery details from customer.io, clarifying what "personalized" means, and examining the MX records for the recipients.
Expert from Word to the Wise explains that sender reputation can influence where emails are placed, even if they're technically delivered. If sender reputation is poor, the recipient's server may filter those emails into junk or quarantine.
What the documentation says4Technical articles
Documentation from Microsoft explains that Exchange Online Protection can accept a message but still filter it post-delivery, moving it to junk or quarantine. It suggests checking these locations if the logs indicate successful delivery.
Documentation from RFC Editor (specifically RFC 5321 on Simple Mail Transfer Protocol) explains that successful SMTP transaction doesn't guarantee inbox delivery. Recipient server can accept the message and later discard or filter it. Full delivery involves policies beyond the basic SMTP protocol.
Documentation from DKIM.org explains if the DKIM signature is invalid, the recipient server may still accept the message, but mark it as suspicious or place it in the junk folder. Properly implement and verify DKIM.
Documentation from Amazon Web Services explains that if logs show successful delivery, the issue might be on the recipient side. Potential causes include aggressive spam filters, incorrect email client configurations, or the email being routed to a less obvious folder. Check recipient-side filtering rules and client settings.