Summary
Emails sent through third-party services like SendGrid often face different deliverability challenges compared to those sent directly from corporate email systems like Office 365. This disparity, particularly when targeting Outlook.com and other Microsoft inboxes, is a common issue for many organizations. The core difference lies in how Microsoft assesses and trusts the sending infrastructure and the sender's reputation associated with each method.
Key findings
- IP reputation: Microsoft (and Outlook.com specifically) is highly sensitive to the IP address reputation. Corporate O365 environments typically have robust, highly trusted IP ranges with low complaint rates, making them less susceptible to blocklisting or junk folder placement. SendGrid, as a shared service, manages a vast pool of IPs, and while dedicated IPs can mitigate some risk, overall IP reputation is influenced by all users on the shared infrastructure (if applicable) or the history of that specific dedicated IP.
- Volume and sending patterns: Office 365 sends typically involve lower, more consistent volumes for individual users, resembling direct human interaction. SendGrid, designed for bulk sending, often handles higher volumes and more automated patterns, which can trigger stricter spam filters if not managed carefully. The volume and frequency of emails can greatly impact whether they land in the inbox or the spam folder.
- Sender authentication: Proper implementation of SPF, DKIM, and DMARC is critical. While a corporate O365 setup inherently handles much of this, SendGrid requires diligent configuration by the sender to ensure these authentication protocols align correctly with the sending domain. Misconfigurations can lead to emails failing authentication checks, a major red flag for recipient servers.
- Complaint rates and engagement: User complaints (marking emails as spam) and low engagement rates (opens, clicks) negatively impact sender reputation. Even with low reported spam rates from the sending service, direct user actions at the recipient end can significantly hurt deliverability. Microsoft's filtering prioritizes user feedback and engagement signals.
Key considerations
- Technical setup: Ensure that SPF, DKIM, and DMARC records are impeccably set up for your domain when sending through SendGrid. Any misalignment can severely impact trust with Microsoft. You can find more details on a simple guide to DMARC, SPF, and DKIM.
- Sender reputation monitoring: Utilize Microsoft's SNDS (Smart Network Data Services) and JMRP (Junk Mail Reporting Program) to gain insight into your sending reputation and complaint rates directly from Microsoft. These tools are crucial for diagnosing deliverability issues with Outlook.com and Hotmail.com.
- Content quality: Review email content for common spam triggers, including excessive links, certain keywords, or poor formatting. While less common for transactional emails, it can affect marketing-style messages.
- List hygiene and engagement: Regularly clean your email lists to remove inactive or invalid addresses, reducing bounces and spam trap hits. Focus on sending to engaged users to maintain a positive sender reputation. Explore why emails are going to spam and how to fix it to improve your overall deliverability.
- Warm-up dedicated IPs: If using a new dedicated IP with SendGrid, ensure a proper warm-up schedule is followed to gradually build its reputation with ISPs, including Microsoft. You can learn more about why your emails are going to spam from Twilio's insights.
What email marketers say
Email marketers often find themselves perplexed when their outbound campaigns, particularly those routed through third-party services like SendGrid, unexpectedly land in spam folders, while direct emails from their corporate Office 365 accounts sail through. This frequently leads to a frantic search for overlooked configurations or hidden reasons, especially when internal spam reports from SendGrid show minimal issues. The perception from the marketing side is often that all emails are failing, despite conflicting data.
Key opinions
- Perceived universal spamming: Marketers frequently report that all emails are going to spam, which may be an exaggeration of a significant, but not absolute, deliverability problem.
- Limited SendGrid reporting: The spam reporting from SendGrid might not align with user complaints, showing only a small number of spam reports even when many recipients claim emails go to junk. This discrepancy makes diagnosis challenging for marketers.
- Internal vs. external sending: There's a noticeable difference in deliverability between emails sent directly from corporate O365 accounts and those sent via a CRM system through SendGrid, even when using the same domain. This suggests that the sending infrastructure plays a crucial role beyond just domain reputation.
- Blaming aggressive sending: Marketers often suspect that their sales representatives are blasting people, leading to complaints and junking, even if SendGrid reports don't fully confirm this.
Key considerations
- Understand the full picture: Don't solely rely on your sending service's spam reports. Implement inbox placement tests and monitor anecdotal feedback from sales reps to get a more comprehensive view of deliverability issues. This is key to how to determine if marketing emails are going to spam.
- Review unsubscribe mechanisms: Ensure your emails sent through SendGrid have a clear and functional unsubscribe link. Missing this can lead to recipients marking your emails as spam instead of unsubscribing, significantly hurting your reputation. The Bubble Forum discusses this as a likely issue.
- Content and engagement strategy: Even with proper technical setup, irrelevant or unwanted content can trigger spam filters. Focus on sending valuable content to an engaged audience to prevent emails from going to spam in 2024. Consider segmenting lists and personalizing messages.
- IP warm-up and monitoring: If using a new dedicated IP, follow a strict warm-up schedule. Regularly check your IP on public blocklists. While your emails might be on a dedicated IP, its reputation still needs careful management.
Marketer view
An Email Geeks marketer shares a common observation, noting that emails sent from their CRM system via SendGrid are consistently going to spam for Outlook.com recipients, even though their direct corporate emails (O365) from the same domain reach the inbox. This highlights a puzzling inconsistency in deliverability based on the sending method.
Marketer view
An Email Geeks marketer recounts testing with their manager, where emails from their CRM (SendGrid) were junked by Microsoft accounts, but direct emails from their corporate O365 account were delivered to the inbox. This stark contrast underscores the distinct treatment of different sending paths by recipient servers.
What the experts say
Email deliverability experts highlight that the difference in spam placement between SendGrid and Office 365 primarily stems from fundamental distinctions in IP reputation and how major mailbox providers, especially Microsoft, perceive these sending sources. While technical configurations like SPF, DKIM, and DMARC are foundational, the underlying volume and reputation of the sending infrastructure play a significant role. Experts often caution against anecdotal reports of all emails going to spam, stressing the need for granular data and a methodical troubleshooting approach.
Key opinions
- Fundamental technical checks: Experts consistently advise starting with verification of SPF, DKIM, and DMARC records, as these are foundational for deliverability, especially for third-party sending services.
- Monitoring tools are crucial: Access to SNDS (Smart Network Data Services) and GPMT (Google Postmaster Tools) is essential for monitoring IP and domain reputation, bounces, and spam trap hits. Without this data, diagnosis is significantly hampered.
- O365's inherent advantage: The IP reputation of Office 365 is significantly harder to negatively impact compared to SendGrid, largely due to its massive scale and diverse user base. This makes O365 inherently more trusted by recipient filters like Outlook.com.
- Outlook.com's IP focus: Outlook.com remains more IP-focused in its filtering than some other mailbox providers. Even with a dedicated IP on SendGrid, the overall reputation of that IP and the sending patterns still heavily influence deliverability.
- Skepticism about all email claims: Experts often approach claims of everything going to spam with caution, unless there's a clear, quantifiable cause like a DMARC reject policy or widespread blocklist event impacting the IP.
Key considerations
- Dedicated IP vs. Shared IP: While using a dedicated IP with SendGrid provides more control over your sending reputation, it also places full responsibility for that reputation on your shoulders. Without a dedicated IP, you risk being affected by other users' sending habits on a shared blocklist.
- Volume management: If email volumes are high through SendGrid, especially with lower engagement, scaling back sending might be necessary to improve deliverability to Microsoft domains. This proactive approach helps build or restore a positive sender reputation and prevent email throttling.
- Microsoft's unique filtering: Microsoft 365 and Outlook.com have specific spam filtering nuances, including stricter checks on received headers and alignment. Understanding these can help in optimizing sending practices to reduce junking. More details are available on why Microsoft Outlook.com email deliverability is inconsistent.
- Proactive reputation building: Focus on consistent, high-quality sending to engaged audiences to build a strong IP and domain reputation. This is a long-term strategy for improving deliverability and avoiding blocklists, whether you're on a shared or dedicated IP.
Expert view
An expert from Email Geeks suggests starting any deliverability investigation by reviewing the standard technical elements like SPF and DKIM. They emphasize the importance of having access to monitoring tools such as SNDS and GPMT, along with reports on bounces and spam trap hits, to effectively diagnose issues.
Expert view
An expert from Email Geeks notes that the IP reputation associated with Office 365 is significantly more resilient to damage compared to that of SendGrid. This difference in robustness means O365 can tolerate more varied sending behavior without immediate deliverability consequences.
What the documentation says
Official documentation from email service providers and mailbox operators consistently emphasizes the critical role of sender reputation, authentication, and compliance with best practices for successful email delivery. While third-party sending services like SendGrid provide powerful infrastructure, the ultimate responsibility for maintaining a good sending reputation often rests with the individual sender. Microsoft, in particular, outlines clear guidelines for email senders to ensure their messages reach the inbox, stressing aspects beyond just basic technical setup.
Key findings
- Authentication standards: Documentation from major ISPs like Microsoft explicitly states the requirement for proper SPF, DKIM, and DMARC configuration. These protocols verify the sender's legitimacy and are fundamental to avoiding spam folders.
- Reputation management: SendGrid's own deliverability guides, for example, detail how to maintain a positive sending reputation by managing complaint rates, bounces, and following best practices. This includes warming up dedicated IPs.
- Content and compliance: Official guides often touch on content best practices, avoiding spammy triggers, and ensuring a clear and easy unsubscribe mechanism (list-unsubscribe header) to reduce direct spam complaints.
- Monitoring tools: Microsoft's documentation encourages senders to use SNDS and JMRP to gain visibility into their sending performance and identify potential issues that could lead to emails being junked.
Key considerations
- Aligning authentication: Review SendGrid's documentation on setting up domain authentication, ensuring that your SPF and DKIM records properly authorize SendGrid to send on your behalf. Additionally, ensure your DMARC records are correctly configured and monitored, as issues with DMARC reports from Google and Yahoo (and Microsoft) can indicate underlying problems.
- Sender behavior: Microsoft's sender requirements emphasize positive sender reputation metrics, including low complaint rates and high engagement. Adhering to these guidelines is crucial for improving deliverability, particularly for bulk senders. For detailed steps, refer to how to comply with Outlook's new sender requirements.
- Feedback loops: Documentation often recommends signing up for feedback loops offered by major mailbox providers. These provide notifications when recipients mark your emails as spam, allowing you to identify problematic campaigns or segments.
- Dedicated IP warm-up: SendGrid's deliverability guide explicitly outlines the importance of warming up dedicated IPs to gradually build trust with recipient servers, preventing new IPs from being flagged as suspicious due to sudden high volume.
Technical article
SendGrid Support documentation explains that as a third-party email provider, it must be able to demonstrate permission to relay emails on a sender's behalf. This permission is typically established through proper authentication methods like SPF and DKIM, which are foundational for deliverability.
Technical article
SendGrid Support documentation indicates that when an email is delivered but does not appear in the inbox, it's often because the recipient server accepted the mail but then sorted it into another folder, like spam or a promotions tab. This highlights the distinction between delivery and inbox placement.
Related resources
11 resources
Related pages
Why are my emails having deliverability issues with Microsoft Outlook and Hotmail?
How to prevent emails from going to spam in Microsoft Hotmail or Outlook?
Why is Microsoft Outlook.com email deliverability inconsistent and how reliable is SNDS data?
How To Comply With Outlook's New Sender Requirements
A simple guide to DMARC, SPF, and DKIM
Why your emails fail at Microsoft: the hidden SPF DNS timeout
Understanding and troubleshooting DMARC reports from Google and Yahoo
What happens when your ip gets blocklisted?
Why Your Emails Are Going to Spam in 2024 and How to Fix It
Email Deliverability Issues: Getting Your Messages to the Inbox in 2025
