Mail User Guide
Mail keeps a list of your previous recipients and uses it to suggest or complete addresses for you when you send email. You can delete obsolete or incorrect addresses from the list in Mail.
Apple Mac Address List
Zip it utility for mac. In the Mail app on your Mac, choose Window > Previous Recipients.
Find the address you want to delete. You can search for it or sort the list by clicking a column header.
If you want to check the address in the Contacts app, double-click the card icon in front of the address. If you don’t see a card and want to keep the address in Contacts, just select the address, then click Add to Contacts.
Click Remove From List.
In the Mail app on your Mac, choose Window Previous Recipients. Find the address you want to delete. You can search for it or sort the list by clicking a column header. If you want to check the address in the Contacts app, double-click the card icon in front of the address. MAC addresses will change daily for each device-network pairing and need to be unpredictable to network observers, but can't be the same as other devices' current set of MAC addresses. MAC addresses are formed according to the principles of two numbering spaces based on Extended Unique Identifiers (EUI) managed by the Institute of Electrical and Electronics Engineers (IEEE): EUI-48, which replaces the obsolete term MAC-48, and EUI-64. Also you could use a network tool such as nmap with the option -A, -O, or -sV (Active Fingerprinting and service version) and filter Apple mac addresses prefix using a network anylizer. Looking at the service version, port numbers tcp 65xxx being a iphone-sync port, tcp 548 AFP (OS X) will help you to determine OS X version and Hardware but not precisely.
Tip: If you use Smart Addresses, you can remove a recipient from the list when you address a message by clicking the arrow in the address.
Your Previous Recipients list is available on your other Mac computers (with OS X 10.8 or later), iOS devices (with iOS 6 or later), and iPadOS devices where you’re signed in with the same Apple ID and Contacts is turned on in iCloud preferences or settings.
With per-network MAC addresses in iOS 14, will there be user-facing controls to turn this on or off on a network-by-network basis?Apple Mac Address Lookup
Some networks may use DHCP reservations or MAC Access Controls for example and need an unchanging MAC, while for other networks privacy may be the strongly preferred mode for the user.Mac Address For Apple Watch
Also, how are the MAC addresses generated? Is a server involved? MAC addresses will change daily for each device-network pairing and need to be unpredictable to network observers, but can't be the same as other devices' current set of MAC addresses.