Your I.T. on Tap email account(s) have spam filtering enabled by default, with default values on the configuration settings.
However you have complete control over your spam filter - if you choose you can change any of the configuration settings or even disable the filter entirely.
Messages identified as spam will accumulate in your filter throughout the day. Once a day the system will email you a summary of the messages collected in your spam filter over the previous 24 hours - showing the sender and subject line in each case.
To release any message held in the filter just click the Deliver link next to the message. The message will then be immediately sent on to the mailbox it was originally addressed to.
In the example above it is clear that the message 2nd from the top is non-spam and so should be released from the filter.
Once you have released any non-spam messages from the filter, the quarantine summary message can be deleted.
To check your spam filter at any time in between the daily summary messages, or to change your filter settings, log into your message center as follows:

Click the Junk Email Settings and you will have the option of changing your settings, as shown below.

When you scroll down from the settings, your Sender lists will be displayed.

Adding email addresses to the Approved Senders list will whitelist those addresses, so that emails from that address bypass the spam filter in future.
To examine why a message was blocked by the filter, first release the message and open it in Outlook.
Check the message headers by choosing View->Options.

The message headers will be displayed in the Internet headers box. The full list of headers will be easier to read if you copy & paste into Notepad or Word.

Look through the headers for the line that begins: X-pstn-levels, then see this page for an explanation of the fields on that line.