How can I whitelist my  mx server in O365?

SAM2009 used Ask the Experts™

I'm in process to migrate my users mailboxes from Exchange 2007 to O365.

I set a Send Connector rule to send all emails for migrated recipients to O365 MX server. Now  I got a msg from O365 like: #550 5.7.1 Service unavailable, Client host [x.x.x.x] blocked using Spamhaus. To request removal from this list see

Why my Hub Transport is considered as spam? How can I whitelist my server in O365?

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Shreedhar EtteTechnical Manager
Top Expert 2010

Hi Sam,

Which migration approach you are using?
Most Valuable Expert 2015
Distinguished Expert 2018

The blacklist is not with Microsoft but with Spamhaus, as the message above shows. That's where you should unlist it and potentially get an answer why it was blocked.
Server engineer
After removing the exchange server public IP from blacklist you may update the SPF record with exchange server public IP and also include O365 SPF record i.e.

v=spf1 a mx a: ip4: -all

Also you can go to connection filtering in O365 and white-list exchange server public IP.

Sign into Office 365 and click "Admin", then "Admin Centers", followed by "Exchange"
Under the "Protection" list, choose "Connection Filter"
Click the "Edit" button which looks like a pencil
Choose "Connection Filtering" on the left side menu
Click the plus "+" symbol and add an IP range from the list below and click "OK"
Repeat step 5 until the IP ranges below have been entered
Check the "Enable Safe List" checkbox
Finally, click "Save"



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