24056 – Sender rewriting scheme for forwarded emails from Office 365 (archived)

Product:

Exchange, SharePoint

Platform:

Online, World tenant

Status:

Launched

Change type:

Links:

Details:

To combat email abuse, new authentication mechanisms, such as SPF, DKIM, and DMARC, are being used to combat the spoofing of domains by spammers. These mechanisms, however, are not compatible with the way emails have been forwarded from Office 365 to forward addresses set up for hosted mailboxes. More and more, recipient email servers are rejecting forwarded emails coming from Office 365 as the sender address is not for a domain Office 365 is allowed to send as. To fix this issue, a sender rewriting scheme is being rolled out in Office 365 that will change the sender email address to use the domain of the tenant whose mailbox is forwarding the message. This will avoid the rejections taking place by some email servers with strict settings for their SPF checks. Specifically, the Mail From field that email servers use to determine the sender email address will be rewritten. The separate From header which contains the sender address that is shown to recipients in their email client will not be changed. If any forwarded emails fail to be delivered to the forwarded address, the non-delivery responses will be sent to the original sender of the email which has always been the case

Change Category:
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Scope:
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Release Phase:

Created:
2017-10-25

updated:
2019-05-17