Google Message Security for Google Apps Administration Guide - Manual (Page 179)

Spam Filters 179
How spam is handled when it is identified by these filters depends on the spam
disposition defined for the user’s organization. For more information, see
“Configure Spam Disposition for an Organization” on page 176.
Fine-Tune Spam Filters
Adjusting spam filters requires striking a good balance between catching the most
spam possible while not falsely identifying legitimate messages as spam. Do this
at service initiation, and periodically afterwards, to accommodate continual
calibrations that the message service makes to the filtering mechanism.
As you increase filter levels to be more aggressive, you catch more spam, but you
also increase the opportunity for false positives. Users typically prefer receiving a
few spam messages over having legitimate messages tagged as spam, so it’s
best to approach fine-tuning conservatively. The best approach involves repeated
testing, and then monitoring your success after each adjustment.
We recommend the following:
1. Add your company’s customers, vendors, and other common addresses and
domains to your Approved Senders list.
2. Make sure Blatant Spam Blocking is enabled for your orgs, which
automatically blocks the most obvious spam.
3. Before adding users to an org, configure the org’s Default User so the Bulk
Email filter is set to 2 and all Category filters are set to Off. View spam reports
for the org, and get feedback from users to monitor the effectiveness of these
settings.
4. If, after that, too much spam of all types is getting through the filters, increase
users’ Bulk Email filters by one level, and leave all category filters off. Do this
for the org’s Default User to apply to new users, and for existing users via
each user’s Overview page.
5. If a specific category of spam is getting through (such as special offers),
increase the strength of that category filter by one level for all users.
When you go through the configuration process, keep in mind:
• The lower the setting for Bulk Email, the higher a category filter setting must
be to have an appreciable effect.
• Whenever you increase the Bulk Email filter, try resetting category filters to a
low level, and then increase them as needed.
• Make small adjustments as needed. Change only one filter at a time and
monitor results before you make additional changes.
• Raising a category filter’s level rather than the Bulk Email filter level is more
likely to falsely quarantine legitimate messages.