A public zoho mail group (e.g. news@....) has naturally external mail members.
Instead of inviting (= pushing) externals to our group,
we would like to offer externals the possibility to send a dedicated mail which leads automatically to membership
(= pull-principle).
The advantage is that the group membership is not only controlled by group moderators alone,
but additionally by the public, which seems to be a good idea for a public mail group.