If you have an email address listed directly in the HTML code or on a webpage directly (in straight text format) and if you have an obvious email address e.g info@ you will continue to receive a lot of spam.
You can only increase the strength of a filter so far until it starts cutting out real emails so:
1) Create a new email address which isn't obviously guessable by spam software e.g. officeadmin@ or office1@
2) Set up a contact form so that the new email is embedded in the database and can't be viewed by spam software on the website.
3) You will then need to keep checking both the old and the new email, while you phase the new one in. (being careful to only give it out to people you trust), not for instance giving it out to companies that might sell it to spammers somewhere along the line.
If you treat it like your mobile phone number, as in only give it out to those you know and trust then you will receive less.
You will then just need to set up Outlook on his computer to check it.
Any name that is easy to guess will automatically get spam.
Also best to set Outlook so that it does not download images by default, otherwise you can be confirming spam as a successful hit when you view an image on it.
Unfortunately the spam filters only work to a point.