Why suspect mail is not moved into my Junk folder

Why a message you think is spam stayed in your Inbox.

There are two explanations, and they need different answers.

The filter did not consider it spam

Nothing moves a message the filter judged clean. If too much is getting through, see when spam reaches your inbox, and mark the messages yourself so the filter learns. See training the spam filter.

Your mail program is not filing it

A Zimbra mailbox moves suspect mail into Junk for you, so this case does not arise there.

Where our Email Security service filters mail before delivering it to a server of your own, the message arrives tagged but nothing files it. Your mail program has to do that, using a rule you or your email administrator create. See rules for spam filtering in Microsoft Outlook.