Summary
Identifying Microsoft-owned inboxes for exclusion involves a multi-faceted approach combining domain listing, MX record analysis, header inspection, and reliance on external resources. A primary step is utilizing lists of common Microsoft domains (Hotmail, Live, MSN, Outlook) along with their international variations (obtainable from Microsoft Learn or Spamresource). Segmentation within email platforms facilitates easy exclusion. More advanced techniques involve querying MX records to pinpoint mail servers used by Microsoft and analyzing email headers for Microsoft-specific infrastructure signatures. Identifying Office 365 hosted mailboxes is also possible by checking SPF records for 'include:spf.protection.outlook.com'. Microsoft SNDS indirectly assists by providing sending reputation data specific to Microsoft properties. Leveraging Spamhaus, one can compare audience IP's against those associated with Microsoft-related spam activity. Finally, the use of the subdomain syntax (olc.protection.outlook.com, mail.protection.outlook.com, mail.outlook.com) assists in differentiating between types of microsoft email (free, office 365, academic).
Key findings
- Domain Listing: Compiling and maintaining a comprehensive list of Microsoft domains and subdomains is foundational.
- MX Record Analysis: MX record lookups reveal mail servers handling Microsoft email.
- Header Inspection: Analyzing email headers can uncover Microsoft-specific patterns.
- SPF Record Check: Checking SPF records helps identify Office 365 users.
- Segmentation Tools: Segmentation features in ESPs facilitate targeted exclusions.
- Microsoft SNDS Data: Microsoft SNDS information can help identify traffic patterns for Microsoft domains
- Spamhaus Data: Microsoft IP information available on spamhaus can assist with this activity.
- Subdomain Identification: Using subdomain analysis you can find out the type of microsoft email client.
Key considerations
- List Accuracy: Ensure domain and IP lists are up-to-date to prevent excluding valid addresses.
- Maintenance Overhead: Regular maintenance is crucial due to Microsoft's evolving infrastructure and policies.
- Technical Expertise: Advanced methods (MX lookups, header analysis) demand technical knowledge and resources.
- Data Privacy: Compliance with data privacy regulations is essential.
- False Positives: Prevent unintended exclusion of legitimate recipients by validating results
What email marketers say
6 marketer opinions
Identifying and excluding Microsoft-owned inboxes from email audiences can be achieved through various methods. A primary approach is to compile a list of common Microsoft domains (e.g., Hotmail.com, Live.com, MSN.com, Outlook.com) and segment email lists to exclude these domains. Advanced techniques involve querying MX records to identify Microsoft's mail servers and analyzing email headers for patterns indicative of Microsoft infrastructure. Additionally, checking SPF records for 'include:spf.protection.outlook.com' can help identify Office 365 hosted mailboxes.
Key opinions
- Domain Exclusion: The simplest method is to exclude common Microsoft domains.
- Segmentation: Email platforms support segmentation for easy exclusion.
- MX Records: MX record queries reveal Microsoft mail servers.
- Header Analysis: Advanced analysis of email headers can uncover less obvious Microsoft inboxes.
- SPF Records: Checking SPF records for 'include:spf.protection.outlook.com' identifies Office 365 users.
Key considerations
- Maintenance: Microsoft's domains and infrastructure may change, requiring regular updates to exclusion lists.
- False Positives: Advanced techniques may inadvertently exclude non-Microsoft addresses, so thorough testing is essential.
- Purpose: Consider why you are excluding Microsoft inboxes. Is it for deliverability troubleshooting, segmentation, or something else? This will impact the best approach to take.
Marketer view
Email marketer from StackOverflow explains that you can identify if mail is hosted with office 365 via checking spf records which have the include:spf.protection.outlook.com in the spf record.
30 Nov 2022 - StackOverflow
Marketer view
Email marketer from ActiveCampaign explains that you can exclude email addresses by using segmentation. Create a segment that contains the domains you want to exclude.
12 Dec 2024 - ActiveCampaign
What the experts say
7 expert opinions
Identifying Microsoft-owned inboxes for exclusion can be achieved through several expert-recommended methods. Using MX lookups on recipient domains reveals those pointing to Microsoft's webmail MX servers. Queries for domains containing 'hotmail', 'outlook', 'msn', etc., can uncover international variations. Microsoft's free webmail is associated with '%.<http://olc.protection.outlook.com|olc.protection.outlook.com>', while '%.<http://mail.protection.outlook.com|mail.protection.outlook.com>' is for Office365 hosted emails, and '%.<http://mail.outlook.com|mail.outlook.com>' identifies ms_academic accounts. External resources like Spamresource offer regularly updated lists of Microsoft domains and subdomains. Additionally, Microsoft SNDS indirectly helps by providing sending reputation data specific to Microsoft properties.
Key opinions
- MX Lookups: MX lookups identify domains using Microsoft's webmail MX servers.
- Domain Queries: Querying for common Microsoft domains reveals international variations.
- Subdomain Identification: Specific subdomains differentiate between free webmail, Office365, and academic accounts.
- External Lists: Spamresource provides comprehensive lists of Microsoft domains.
- SNDS Data: Microsoft SNDS data indirectly identifies sending to Microsoft properties.
Key considerations
- List Maintenance: Microsoft's infrastructure and domain usage evolve, requiring frequent updates to exclusion lists.
- Data Privacy: Ensure compliance with data privacy regulations when collecting and using domain information.
- Accuracy: Verify the accuracy of identified domains to avoid inadvertently excluding legitimate recipients.
Expert view
Expert from Email Geeks suggests using MX lookups on the list of domains being sent to in order to identify the ones that point to Microsoft's webmail MX.
5 Sep 2023 - Email Geeks
Expert view
Expert from Email Geeks shares that %.<http://olc.protection.outlook.com|olc.protection.outlook.com> is for Microsoft's free webmail and %.<http://mail.protection.outlook.com|mail.protection.outlook.com> is for Office365 hosted emails.
9 Feb 2024 - Email Geeks
What the documentation says
4 technical articles
Identifying Microsoft-owned inboxes can be achieved through several documented methods. Microsoft Learn offers a comprehensive list of Microsoft email domains, including country-specific variations. The IETF describes using MX record lookups as a standard way to determine mail servers responsible for a domain, which can be used programmatically to identify Microsoft inboxes at scale. Spamhaus notes that some Microsoft IP ranges are associated with spam activity, allowing for identification of problematic inboxes by comparing against known spam sources. Finally, PowerDMARC mentions SPF records as a security mechanism, useful contextually, although its direct application to identifying Microsoft inboxes isn't explicitly stated in the provided context.
Key findings
- Domain List: Microsoft Learn provides a detailed list of Microsoft email domains.
- MX Records: IETF documents MX record lookups as a standard identification method.
- IP Ranges: Spamhaus identifies some Microsoft IP ranges as associated with spam.
- SPF Records: PowerDMARC highlights SPF records as a domain security mechanism.
Key considerations
- Maintenance: Domain lists and IP ranges require regular updates to remain accurate.
- False Positives: Relying solely on IP ranges may result in false positives; consider combining methods.
- Technical Expertise: Programmatic MX record lookups require technical expertise and infrastructure.
Technical article
Documentation from Spamhaus explains that some Microsoft IP ranges are associated with spam activity. Comparing your audience's IP addresses against known spam sources can identify potentially problematic Microsoft-owned inboxes.
29 Feb 2024 - Spamhaus
Technical article
Documentation from Microsoft Learn shares a detailed list of all public Microsoft email domains, including country-specific variations. This is intended for developers but can be used to compile a comprehensive exclusion list.
6 Apr 2025 - Microsoft Learn
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