Below are the steps to set up a mail flow rule to bypass Safe Attachments Processing.

1. In the Microsoft 365 Exchange Admin Center, create a new mail flow rule 
2. Give the rule a name, e.g. Bypass Safe Attachments.
3. Click More Options.
4. From the 'Apply this rule if…' drop-down, select the senders, followed by IP address is in any of these ranges or exactly matches. 
5. Enter our IP addresses. (Please refer to IP Addresses for the most up-to-date list.)
6. From the 'Do the following…' drop-down, select Modify the message properties..., and then set a message header.
   • Click the first *Enter text... link and set the message header to: X-MS-Exchange-Organization-SkipSafeAttachmentProcessing
   • Click the second *Enter text... link and set the value to 1.
7. To finish, click Save.