Spam email that is not spam

[#1]

I've a spam email box set up which thanks to plusnet has worked like a dream for the past year, it catches all those unwanted emails (plus a few I did want).
Only one issue "How do I get a potential spam message that is not spam" to come in as normal email.
I highlight the message (tick the box), hit the 'not spam' button and nothing happens, the following month the mail still crops up as spam

[#2]

HI journeys,
Selecting that option is not an automatic tag and the spam system will only change it if it gets enough of the same address marked as not spam. You can whitelist this address yourself via manage my mail in your account. A friendly link to the very page you need is here.
Hope that helps,
Jojo

[#3]

Thanks Jojo, tried your link, I get the following message
Unfortunately, this feature is not available with your current account. To raise any queries and to upgrade your account....................
Not sure I want to upgrade my account

[#4]

Hmm, ok let me have a look...

[#5]

Ahh, ok. Sorry. If you go to http://email.plus.net and click the spam tab you can do it from there

[#6]

Jojo:- thankyou