Sender Rewriting Scheme Coming to Office 365

Microsoft have announced Sender Rewriting Scheme which is coming to Office 365!

The introduction of email authentication mechanisms like SPF, DKIM and DMARC now have improved email security and spoofing prevention. There have however been scenarios that have been disruptive by these mechanisms one of which is auto-forwarding and relaying.

From 16th July 2018 Microsoft will begin to roll out the Sender Rewriting Scheme, this is to solve the ongoing problem of auto-forwarding being incompatible with SPF. The SRS feature works by rewriting the envelope from the address for all applicable messages sent externally from Office 365. The ‘from’ header which is displayed by email clients will remain the same. The change to this system will improve the deliverability of messages since SPF checks that had been failing previously will now pass. The following scenarios will be result in SRS Rewriting the envelope from the address:

  • Messages that are auto-forwarded or redirected from hosted mailboxes using one of the supported methods – SMTP forwarding, Mailbox Rule or inbox rule redirection, Transport Rule redirection.
  • Messages that are auto-forwarded or redirected from customer’s on-premise environments and relayed through Office 365.

SRS rewriting would also rewrite the envelope from the address of messages that are relayed from customer’s on-premise environments where the envelope from domain is not a verified domain. Customers should only be sending messages from domains in their Accepted Domains lists.

This change results in Non-Delivery reports returning to Office 365 instead of the original sender as it occurs now without SRS.


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