Help for the Recipient Options Form

See Border Patrol MTA {tm} for a diagram and general explanation of how we process your email.
            CheckID Options

- Whitelist Threshold
The default is to whitelist any senders with a rating better than 10.  That is less than one spam in every 10
emails.  Messages from whitelisted senders go straight to your inbox, with no delay or risk of loss in the
spam filter.  One in ten seems to be a reasonable compromise for most recipients.  That will include
B-rated domains that may be new and haven't had time to earn an A-rating.  If you want only A-rated
domains on your whitelist, set your threshold to 100.

Any mail from senders that don't offer authentication of their ID, or that don't have a rating above your
threshold, will be "brownlisted".  None will be "blacklisted" unless they are specifically on your blacklist.  All
brownlisted mail goes to the spam filter.
             Filter Options
- IP Blackist
This is where we do the standard rejection of blacklisted IP addresses.  The default choice is a moderately
aggressive blacklist.  This is a good compromise between keeping your inbox clean and minimizing false
rejects of legitimate mail.  Other choices include "conservative" (less false rejects) and "aggressive" (less

- Ham Threshold
The default is set at 50.  Any message with a spam score less than 50 is most likely ham, and will be
tagged with a single [*].  See
spam scores below for more detail on how our spam filter scores a message.
Note:  If you want to bypass the spam filter entirely, set your ham threshold to 100.  This may be useful if
you run a filter on your own machine, trained to your individual mail flow.

- Spam Threshold
The default is set at 55, which will tag the "best 10%" of the spam with the [**] unsure label.  Any message
with a score greater than 55 is almost certainly spam, and will be tagged with [spam].  This default setting
is intended to err on the side of no false rejects.  As you gain more confidence in the ability of the filter to
make a sharp distinction between ham and spam, you may want to lower this threshold.

- Subject Line Tagging
Whitelisted messages are tagged with [ ].  Brownlisted messages (any that go to the spam filter) are
tagged with
[*], [**], or [spam].  Occasionally, you will see a [-] tag.  These are messages that
were not whitelisted, but did not go to the spam filter, usually because they were too large, or maybe there
was an authentication failure on our end, and we accepted the message just to be safe.

Most recipients find these tags a helpful visual guide, but they are not really necessary.  You can sort your
mail into different folders using the X-SpamScore header.  See the main
info page for how to use these

- From Line Tagging
When a domain name in the From header differs from the domain of the actual sender, we add a [!] tag
on the From line.  This is a simple check, not intended to take the place of a more robust anti-phishing
authentication method.  You can turn this OFF if you prefer.

- Discard Spam
If you never look at the messages in your [spam] folder, you might as well not even download them.  
Change this option to YES, and we will discard any message with a score higher than your Spam

- Enable SpamCooker
This will send a challenge to senders that authenticate properly, but don't meet your whitelist threshold,
and end up in your "unsure" bucket.  These will be forwarded to the SpamCooker service, and they will
accept or reject the sender.  You can then decide whether to add the sender to your individual whitelist.
Note: We do not send challenges to all the senders of "unsure" messages, only the ones we can
authenticate.  This avoids the "bounce spam" that plagues many challenge/response systems.

- Block Solicited Commercial Email (SCE)
Senders of legitimate bulk mail, i.e. those that have an "opt-in" policy, and are doing everything right, still
get many spam reports from recipients who may have forgotten they signed up for a mailing list.  Their
ratings are low compared to domains that send no bulk email.  
Bulk mail will be rated on a different scale
than First Class mail, and will be tagged [sce], so you can easily sort it into a different folder.  If you wish to
receive no bulk mail at all, check this option.
 You can still include a specific sender's domain in your
individual whitelist
(see below) even if it would otherwise be blocked by this option.
            Spam Scores

Most spam filters provide a raw score indicating the "probability" that a message is spam.  Typically there
will be a
bimodal distribution in raw scores, having a lump of ham with low scores, and a bigger lump of
spam with higher scores.

.                         *
.                        ***
.  **                   *****
. ****  *    *     * * ******
.             2.5                   raw score

The raw score won't mean much to a recipient. To simplify the user interface, this raw score is stretched
and distorted so that the final score is evenly distributed in the range 0 to 50 for ham, and 50 to 100 for
spam.  The 50 point is chosen halfway between the two lumps, and can be easily understood as the
point where there is equal probability that a message is spam or ham.

.               *************
0             50           100      final score

A recipient who wants to send the "best half" of the spam to his "unsure" folder, can set his thresholds at
ham <50 and spam >75.  The spam threshold can be lowered as more confidence is gained in the ability of
the filter to make a sharp distinction between ham on the left and spam on the right.
     Whitelists, Blacklists, Brownlists

These lists allow you to change the handling of mail from individual domains.  The most useful will likely be
the whitelist.  If you are expecting mail from someone whose domain might have a rating lower than your
threshold, you can force the whitelisting of that domain regardless of its rating.

The blacklist is useful for the rare situation where you are getting a lot of spam from a particular domain,
but for some reason, nobody else is seeing it, and they continue to have a good rating.

The brownlist is for the same rare situation, but instead of simply blocking the mail from that domain, you
would rather send it to the spam filter.

Eventually, the need for these lists will go away, and any sender that is honest and competent will have an
To Do:
- fix links

DRAFT 13-Aug-07