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Summary

Even when SendGrid reports transactional emails as delivered, they may not appear in the recipient's Outlook inbox. This often occurs due to Microsoft's filtering mechanisms, which can re-route messages to junk or other folders, or even silently drop them without an explicit bounce (a phenomenon sometimes called "ghosting"). Unlike bulk marketing emails, transactional emails are often expected to land in the primary inbox, making their absence particularly problematic.

What email marketers say

Email marketers often face challenges with transactional emails not appearing in Outlook inboxes, despite SendGrid's successful delivery reports. This issue frequently points to an underlying reputation problem with the sending IP or domain, or specific content triggers that Microsoft's filters flag as suspicious. Many marketers suggest that slight variations in content, even for emails with the same subject line, can have a significant impact on deliverability to Microsoft properties.

Marketer view

Email marketer from Email Geeks suggests that Microsoft often performs a "ghosting" action for higher-risk mailers, like inactivity notices. This means the email is delivered but hidden from the inbox.

22 Jan 2021 - Email Geeks

Marketer view

A marketer from Bubble Forum states that SendGrid's IP has been blocked by various email services, causing transactional emails not to reach users. They suggest exploring alternative email service providers.

10 Jan 2022 - Bubble Forum

What the experts say

Email experts agree that a delivered status from an ESP like SendGrid does not guarantee inbox placement, particularly with Microsoft. They emphasize that local transport rules at the recipient's server or specific content issues are often culprits when only certain emails are affected. The broader reputation of the sending service, even with dedicated IPs, can also play a role, as can evolving sender requirements from major mailbox providers.

Expert view

Expert from Email Geeks suggests that if an issue is verified to be occurring with only a single recipient domain, then local transport rules on that domain's mail server are likely the cause of the email not appearing in the inbox.

22 Jan 2021 - Email Geeks

Expert view

An expert from SpamResource emphasizes that email deliverability is complex, and even when an email is accepted by the recipient's server, various internal filters can still divert it from the primary inbox without generating a bounce message.

10 Apr 2024 - SpamResource

What the documentation says

Official documentation from email service providers and mailbox providers consistently clarifies that a "delivered" status does not guarantee inbox placement. Receiving servers often perform additional filtering after accepting a message, based on a multitude of factors including sender reputation, content analysis, and compliance with authentication protocols like SPF, DKIM, and DMARC. Outlook, in particular, has stringent requirements that can lead to emails being filtered if they do not meet compliance or engagement standards.

Technical article

Documentation from SendGrid states that the "delivered" event fires when an email is accepted at the receiving server. However, this event does not guarantee that the email was placed in the recipient's inbox, indicating that further processing and filtering may occur.

22 Jan 2021 - SendGrid Support

Technical article

Documentation from Twilio (SendGrid's parent company) indicates that Outlook is implementing new sender requirements which mandate SPF, DKIM, and DMARC compliance. Non-compliant messages will initially be delivered to the junk folder.

01 Jan 2024 - Twilio Blog

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