Why does Office 365 hosted exchange use 25.x.x.x IP addresses?

Discussion in 'Office 365' started by popowich, May 6, 2015.

  1. popowich

    popowich EQ Forum Admin Staff Member

    Aug 12, 2008
    Likes Received:
    It was recently reported that users of the Office 365 exchange service are seeing 25.x.x.x IP addresses in their full email headers.

    As far as I can tell, these addresses may be used "internally" by Microsoft, but are not used for relaying email to other service providers.

    I came to that conclusion because the IP addresses I checked from the full headers of emails do not have a sender score, for example:

    Lookup for - SenderScore.org

    The lack of PTR records or mention of Microsoft in a whois lookup is interesting:

    OrgName: RIPE Network Coordination Centre
    OrgId: RIPE
    Address: P.O. Box 10096
    City: Amsterdam
    PostalCode: 1001EB
    Country: NL
    Updated: 2013-07-29

    Update: A Microsoft rep commented that this address range is used for Microsoft Exchange Online Protection (EOP) service.

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