Sender Rewriting Scheme (SRS) functionality in Office 365
To combat email abuse, new authentication mechanisms such as Sender Policy Framework (SPF), DomainKeys Identified Mail (DKIM), and Domain Message Authentication Reporting and Conformance (DMARC), are being used to combat the spoofing of domains by spammers.
This new sender rewriting scheme in Office 365 will change the sender email address to use the domain of the organization whose mailbox is forwarding the message. This will avoid rejections 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.
Beginning mid-July, Microsoft will begin rolling out Sender Rewriting Scheme (SRS) functionality in Office 365 to improve auto-forwarding compatibility with SPF.