filter
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... This memo documents a language that can be used to create filters for
electronic mail. It is not tied to any particular operating system ...
... language is powerful enough to be useful but limited in order to
allow for a safe server-side filtering system. The intention is to
make it impossible for users to do anything more complex (and
dangerous) than write simple mail ...
... make it impossible for users to do anything more complex (and
dangerous) than write simple mail filters, along with facilitating
the use of GUIs for filter creation and manipulation. The language ...
... simple mail filters, along with facilitating
the use of GUIs for filter creation and manipulation. The language is
not Turing-complete: it provides no way to write a loop or a function
...
...
There are a number of reasons to use a filtering system. Mail
traffic for most users has been increasing due to increased usage of
...
...
Experience at Carnegie Mellon has shown that if a filtering system is
made available to users, many will make use of it in order to file
messages from specific users or mailing lists ...
... messages from specific users or mailing lists. However, many others
did not make use of the Andrew system's FLAMES filtering language
[FLAMES ...
...
Because of the expectation that users will make use of filtering if
it is offered and easy to use, this language has been made simple
...
... can be used productively. However, it is expected that GUI-based
editors will be the preferred way of editing filters for a large
number of users.
...
... Tests MUST NOT have side effects. That is, a test cannot affect the
state of the filter or message. No tests in this specification have
side effects, and side effects are forbidden in extension tests as
well.
...
...
Previous experience with filtering systems suggests that cases tend
to be missed in scripts. To prevent errors, Sieve has an "implicit
keep".
...
... the error, and it SHOULD contain additional text alerting the
original sender that mail was refused by a filter. This part of the
MDN might appear as follows:
...
...
------------------------------------------------------------
Message was refused by recipient's mail filtering program. Reason
given was as follows:
...
...
The "keep" action is whatever action is taken in lieu of all other
actions, if no filtering happens at all; generally, this simply means
to file the message into the user's main mailbox. This command
...
... email address to contact for further information:
See the discussion list at ietf-mta-filters@imc.org.
Intended usage:
COMMON
...
...
#
# Example Sieve Filter
# Declare any optional features or extension used by the script
#
...
... Users must get their mail. It is imperative that whatever method
implementations use to store the user-defined filtering scripts be
secure.
...
... proofreading. I am grateful to Carnegie Mellon University where most
of the work on this document was done. I am also indebted to all of
the readers of the ietf-mta-filters@imc.org mailing list.
...