Exchange transport rule

Copper Contributor


I been beating my head against the wall trying to get this. 


scenario: My company want to block all attachments that are sent internally. 

               Attachments can be sent externally.


now the sticky part

SO, I need to craft a transport rule or rules that would allow internal senders to to send attachments to both internal and external but only if they are addressed to both.




5 Replies

@Ratpick from your exchange admin center, navigate to Mail flow --- Rules -- Create a new rule and set the following settings as per the screen shot and set the rule to be enforced. 


this rule will block any attachments sent internally between the users. 



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thanks eliekarkafy I can block the attachments internally no issues. My rule blocks my internall attachments and allows external attachemtns. My company want to be able to block all internal attachments unless they include and external address. So I need the the rule to block all internal attachment unless there is a external address. Then the attachment needs to be delivered to both. Internal and External.
add to your rule that is blocking your internal attachments. a condition except if the recipient is an external outside the organization and test it. in that case if one of the recipients is an external the rule will not block the attachment


try to check first one . it might work with you,

is it possible to create a group of the contact of the outside people it will help in filtering the policy. will make it as the second rule (except the to or cc contain any member of this group)






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You could add a rule that blocks the message when the message contains an attachment and the recipient is internal with an exclusion for when the recipient is external. My suspicion is that this won't work as the message is usually exploded for all recipients so the rule runs against all the messages as part of the chain (so the rule will block the internal massages but allow the external ones when both external and internal recipients are included). I could be wrong though, so worth testing.