((mail-from != OR (rcpt-to != 'example\. If the addresses don't match, contact the recipient (by phone, in person, etc.) and ask them if they've configured an email rule that forwards incoming email messages from you to another destination. If the office 365 servers are dynamic then you would need to add the required subnets along with the below message filter to prevent other domains from relaying emails through the ESA. Compare the recipient's email address in the NDR with the recipient's email address in the message in your Sent Items folder. In order to allow emails from the Office 365 to be sent outbound you would need to add the office 365 IP to the HAT RELAYLIST under Mail Policies -> HAT Overview.Īdding this would then treat those emails as outbound and would process as per the outgoing mail policies including content filters and DLP.

Email sent from Office 365 to external (internet) routes through on-prem ESA and normal content filter,outbound mail policy and DLP policy applies.

Email bounce back message in office 365