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 25.161.223.18 - 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
StateProv:
PostalCode: 1001EB
Country: NL
RegDate:
Updated: 2013-07-29
Update: A Microsoft rep commented that this address range is used for Microsoft Exchange Online Protection (EOP) service.
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 25.161.223.18 - 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
StateProv:
PostalCode: 1001EB
Country: NL
RegDate:
Updated: 2013-07-29
Update: A Microsoft rep commented that this address range is used for Microsoft Exchange Online Protection (EOP) service.