David,
? ? ? ? ? ?Juno is an email service provider.? ?Groups.io is not, it is an e-mail list management service (with a concurrent web interface).
? ? ? ? ? ?Email service providers, and only email service providers, decide what they will and will not do as far as central spam filtering.? The page referenced clearly, very clearly, states this and even gives a list (not definitive) of email service providers who are using the mechanisms that result in unwanted unsubscriptions, and why Groups.io must honor those "requests" or face even worse issues.
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Brian - Windows 10 Home, 64-Bit, Version 1803, Build 17134
???? I do not feel obliged to believe that the same God who has endowed us with sense, reason, and intellect has intended us to forgo their use.
? ? ? ? ?~ Galileo Galilei
