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Summary

The question of whether specific 'matching IDs' improve email deliverability to Microsoft accounts, such as Outlook and Hotmail, is a common one among email marketers and deliverability professionals. While some might recall discussions around such identifiers, especially in the context of email analytics platforms, the consensus from experts and industry documentation indicates that these IDs generally do not directly influence inbox placement or sender reputation with Microsoft.

What email marketers say

Email marketers often seek any advantage to improve inbox placement, particularly with major providers like Microsoft. While the idea of a 'matching ID' might sound like a technical tweak for better deliverability, marketers generally agree that such custom headers are not recognized by Microsoft's filtering systems as a factor for inbox placement. Their focus remains on established email marketing best practices and compliance with ISP requirements.

Marketer view

Email marketer from Email Geeks indicates that they initially thought matching IDs were important, having seen information about them somewhere, but couldn't locate specific documentation to support the claim. They were curious if this belief held any merit for Microsoft accounts.

15 Nov 2018 - Email Geeks

Marketer view

Email marketer from Email Geeks mentioned they were updating a significant amount of documentation for email processes and wanted to confirm whether including matching IDs was a necessary step for Microsoft deliverability. If not, they would omit it to streamline their procedures.

15 Nov 2018 - Email Geeks

What the experts say

Deliverability experts generally agree that custom matching IDs, often used for analytics or internal system tracking, do not play a role in how Microsoft's filtering algorithms assess email legitimacy or influence inbox placement. Their algorithms are sophisticated and prioritize standardized authentication, sender reputation, and user engagement metrics over proprietary header information.

Expert view

Deliverability expert from Email Geeks states definitively that custom matching IDs (like rpcampaign:abc123) are not a factor for email deliverability to Microsoft accounts. They are unique to a specific platform's reporting and offer no external benefit.

15 Nov 2018 - Email Geeks

Expert view

Deliverability expert from Email Geeks indicates that it's highly unlikely any Mailbox Providers (MBPs) would give weight to a random X-header, as these are typically for internal reporting. They would be surprised if such headers impacted deliverability.

15 Nov 2018 - Email Geeks

What the documentation says

Official email documentation, including RFCs and major mailbox provider guidelines, consistently emphasizes standard internet protocols for email transmission and authentication. There is no mention of custom 'matching IDs' playing a role in deliverability. Microsoft's own documentation focuses on adherence to industry standards like SPF, DKIM, and DMARC, along with sender best practices to ensure messages reach the inbox.

Technical article

Official documentation from Microsoft TechCommunity states that compliant senders often experience improved deliverability, fewer bounce-backs, and stronger brand credibility. Their focus is on core authentication and sender reputation, not custom IDs.

25 Apr 2025 - Microsoft TechCommunity

Technical article

Documentation from DuoCircle advises that best practices to meet Microsoft's authentication requirements include setting up DMARC and ensuring SPF or DKIM records align with the domain in the 'From' address. This highlights the importance of standard authentication over custom identifiers.

07 Jul 2025 - DuoCircle

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