For reference, this is the issue. iOS devices on some iOS 14 builds will randomly reply with an ARP message sourced from the expected MAC address, however the ARP payload will contain a different source MAC address. The MX will detect this potential conflict (in this example, MAC ending in ad:e0) and send an email alert. This issue seems to be reported regardless of whether MAC randomization AKA "private address" is enabled on the iOS device. [edit]: Once we have updated the devices to iOS14 beta 3, we have not observed this behavior at all. [edit 2]: Photo edited to clarify
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