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Andy MFlag for Croatia

asked on

O365 ant-spam

sender trying to send us 200 e-mail messages at once and we recived only about 20 e-mail messages.
Both sender and recipients are O365 but different organization(tenant)
Sender receive this error message:
Remote Server returned '550 5.1.8 Access denied, bad outbound sender AS(42003)' Original message headers: Received: from
I'm admin for recipients tenant and if I do message trace only 20 e-mail messages are visible from this sender and 180 are not visible in message trace.
Any idea how to trubleshoot this?Bulk problem?
Is it sender or recipient tenant problem?

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My default outbound policy is

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And default inbound

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I'm not sure what those number means

Increase the 0 to a value which meets your your organizational requirement.