You really should look at getting the training for the spam filters, but there is a way to override.
Have a look at this bug:
Bug 34059 – Disable filtering per account / domain / cos
I believe the property you want to set for the user is amavisBypassSpamChecks but I'm not sure exactly. As the bug hints at, you can find a list of the properties possible by looking at the file /opt/zimbra/conf/attrs/amavisd-new-attrs.xml. If my guess right right, it's something like:
Code:
zmprov ma user@doamin.com +amavisBypassSpamChecks TRUE
According to the bug, this can also be done on a cos/domain level as well.