7.6 How should I configure the junk filter on my mail server?

SpamSieve moves the spam messages that arrive in your inbox into a separate mailbox, usually called Junk. When you train a message as spam, SpamSieve also puts it in that mailbox. You may find that other messages also go to the Junk mailbox. These spams were likely caught by a junk filter on your mail server. The server filter catches its spam messages before the Mac sees them. You can tell whether the messages were moved by SpamSieve because of their coloring and because the Log will say that SpamSieve predicted them to be spam.

Spam in Other Locations

A server junk filter may also move spam messages to a separate Spam or Bulk mailbox. The Setting the Junk Mailbox in Apple Mail section describes some ways to make sure that SpamSieve and other filters put the spam messages in the same place. If you prefer to have the server filter use a different mailbox:

It is normal for some spams to be in the server’s spam mailbox rather than SpamSieve’s or to be in the same mailbox as SpamSieve’s spam but unmarked. SpamSieve never had a chance to process these messages, so they are not mistakes. You should not train them as spam.
It is normal for there to be some good messages in the server’s spam mailbox. These are also not SpamSieve mistakes, since the server filter put them there without SpamSieve seeing them. You should not train them as good.

SpamSieve vs. Server Filters

SpamSieve is compatible with junk/spam filters that run on the mail server, however we recommend that most users turn them off because:

In most cases, SpamSieve will catch the same spam messages (and more), so the server spam filter is not providing much benefit. Exception: If your Mac and SpamSieve will often be off or disconnected from the Internet, the server spam filter can help keep spam off your iPhone during that time.
Server spam filters are more likely to mistakenly classify your good messages as spam. Because the server filters the messages before they get to your Mac, SpamSieve cannot “save” you from these mistakes. In some cases, these good messages may be deleted sight-unseen or “lost,” only visible when you log into a special spam quarantine mailbox via a Web browser.

Turning Off Your Server-Side Spam Filter

Please find the “Turning Off” section below that corresponds to your mail provider. Note that some mail hosts, such as Media Temple, have both per-account and per-user spam filters, so there may be more than one switch to turn off.

If your mail provider does not let you turn off its spam filter:

You may be able to at least turn down the sensitivity of the server filter, to reduce the problems that it causes.
You can follow the Rescuing Good Messages Caught By a Server Filter instructions to have SpamSieve look for good messages in the Junk mailbox and move them back to the inbox.
We recommend switching to one of the Recommended Mail Hosts or another host that does provide this level of control.

Bulk Mail and Quarantine

Some mail providers have a mailbox called Bulk Mail or a special Web site to view messages that are “quarantined.” If possible, we recommend turning off these features for the same reasons described above. Regardless, there are two important points to keep in mind:

The server puts the messages in the bulk mailbox before SpamSieve sees them. Thus, there is no setting you can change in SpamSieve to prevent this from happening.
Since these messages are invisible to SpamSieve, it is not necessary or recommended that you train it with them.

If you cannot turn off your server’s Bulk Mail mailbox, you can use the Apple Mail - Server Junk Mailbox script to have SpamSieve sort through the bulk mail for you.