In my zimbra installation I used the command
zmprov md domain.com zimbraMailCatchAllAddress @domain.com zimbraMailCatchAllCanonicalAddress @example.com
to masquerade the internal address with the public one.
The problem is that it does it always, even when I send a mail from
user@mail.local to
user2@mail.local.
If user2 press reply, it will send the mail to
user@publicdomain.com instead of
user@mail.local.
Is there the possibility to use the masqueranding when I send mail to any domain but mail.local?
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Email masqueranding only when neccesary, how to? 
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