[Mailman-Users] Question on Umbrella lists

[Tenant]

I'm still using Mailman 2.0 beta - never bothered upgrading as it works 
fine as a one-way newsletter list. Waiting for 2.1.

I understand the concept of Umbrella lists. We run several lists and the 
membership across the lists runs about 10% -- meaning about 10% of one list 
is also on a second list. Sometimes we wish to send the same information to 
both lists, hence the idea of an umbrella list. I guess the question is 
will that 10% who are members of both lists receive both messages or just 
one? We're a little worried about duplication. Some people still get mad at 
things like that not knowing there's such a thing as a delete key.
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