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...the table can be permissioned as appropriate (probably fine to restrict it to admin). Might be nice to restrict the u_email field to be unique, but that's just icing since it's enforceable manually by any reasonable admin.==

Configuring

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The mail alias binding to groups happens at the Group level in Adminstration controls. Click a group, and then bottom of the dialogue page contains a tab called "Group Email Alias".

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