No spam filter is yet 100% accurate - inevitably some spam will get through and some legitimate emails may be mistakenly filtered out as spam.
If we've marked it as spam it will be in the Junk folder in your webmail. To remove the identification as spam right click on the email and select Not junk.
If it's been added to your junk or spam folder in your email client you'll need to change the setting in your mail client. Usually you can do this by right clicking on the email and marking it as not spam or not junk.