This is fairly technical, but I've gotten some questions on the order of operations a message takes when it is delivered. so here you go:

The flow of mail once it has entered the spool is like this:

1. Delivery delay
2. Any command line executable that was specified will run
3. Spam checks are run
4. Local deliveries

a. Spam filtering
b. Domain level content filtering
c. User level content filtering
d. If target mailbox has a forward – that forward address is added to internal list of SmarterMail recipients
e. Message delivered to target mailbox
f. If target mailbox has an autoresponder the autoresponse message as added to the spool

5. Remote deliveries

Note that there is no level to the spam filtering like there are to content filtering. The global admin can have spam filtering setup which the domain admin can (if allowed) override which the user can (if allowed) override but only one set of spam filtering settings will be used. If the spam filters redirect a message in any way, the message will not get processed further by the target addresses domain or user level content filters. If the message headers are altered by the spam filters, the message will continue to get processed by the content filtering of the target address.

If any content filter is triggered at either the domain or user level regardless of the action, the content filter actions are taken for that filter and no more content filtering is done.

Note that Delete is the last action taken if you check all the options. So it will redirect, bounce, move to folder etc., before being deleted (it doesn't make sense to Move to Folder then Delete though).

A note on this - Smartermail does it's filter operations BEFORE forwarding, however if you have your filter set to deliver messages to the Junk Email folder, that counts as a delivery and is forwarded as well. You can get around this in your settings by setting it to forward messages that DO NOT get marked as Low/Med/High Spam.

What happens with email that is addressed to an alias (as opposed to a user)? In SmarterMail 2.0, messages to aliases were not subjected to filtering (domain content filtering or domain spam filtering). Has this changed in 3.0? I would love that feature -- now I have to create a user corresponding to each alias, and forward from the user to the alias, so that the messages are filtered.

Sorry I missed this when it was first posted - Smartermail 3.x addresses this and aliases now get filtered - the filter operation still happens upon delivery.

When you say "the filter operation still happens upon delivery", do you mean it only works with aliases that resolve to smartermail users? Or should the filter be applied to smartermail aliases which contain non-smartermail users?

It still doesn't seem to work in the latter case. I have a domain content filter that is applied correctly on email to users, but not to aliases. I can send details if you'd like.