Root directly incoming mail into "Public Folder" subdir

[Patrick Lin]

hello
i am running imapd 2.0.12 and  Sendmail Switch-2.1.0
i want to know the best way to root incomaing mail directly to a subdir
of "Public folder"

1 - sieve
2 -  alias 
3 - something else 

and if someone can tell how to do it.

best regards
patrick
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