GMail has a 'Select Contacts' option on its Compose, which brings up your
Contacts as a table with a checkbox on each row and a Select All button so
presumably ( I have not *tried* it ) would let you send a mass mail to a
lot of BCc:ed recipients.
The GMail account will let you Import contacts as a CSV file or VCard from
other mail apps.
So you can probably set up a GMail acct to do what you want. It may not
sound very businesslike though.
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