Running a shell command while saving messages to mailboxes

[Sébastien Hinderer <Sebastien.Hinderer@xxxxxxxxxxxxxx>]

Dear all,

Is it possible to pipe a message throuhh a shell command when saving it
to a mailbox ?
The aim is to feed spamassassin automatically with all ham messages as
soon as they are saved to a milbox which is not =spam.
This would avoid having to call sa-learn regularly on several mailboxes,
which is anyway something non-trivial (atleast for me) as soon as
mailboxes ar stored in maildir format.

Any help sincerely appreciated.
Many thanks in advance,
Sébastien.