If you find a message wrongly classified as spam, you can unmark the message. Training Google to identity spam correctly is easy and best done in GWA** (don't worry, Google learns quickly!).
If you cannot find the Spam folder, scroll to the bottom of your folder list and click More to see "hidden" labels.
Just select the message in your Spam folder, and click the Not Spam button that appears at the top of your current view. The message will automatically move to your INBOX.
If you want to make the Spam folder appear with your other folders by default, click on the gear icon at the top right of the window and select Settings. Select the Labels tab and click show under Show in label list for the Spam label.
If you find that some senders' messages are consistently being mislabeled as spam, you can prevent this by adding their email addresses to your Contacts list. Google will deliver messages from members of your Contacts list to your INBOX, unless they know with high confidence that they are spam.
Some messages sent from contacts which are very clearly spam can be sent directly to your Spam label. More importantly, in some cases messages from contacts will not be sent to Spam but will be marked with a red warning banner if the content is suspicious - for example, your friend's or contact's account has been compromised and used to send phishing messages.
To add a new contact, click Mail in the top left corner and then Contacts.
Click the New Contact button in the top left corner. Enter your contact's information in the appropriate fields, Any information you add will save automatically.
Email addresses are automatically added to your Contacts list each time you use the Reply, Reply to all, or Forward functions to send mail to addresses that don't already exist in your Contacts list.
**Train Google to identify spam by using GWA, Outlook with GASMO, and the Gmail apps for the iPhone or Android. Other email clients - such as Thunderbird, Apple Mail, Outlook for Mac, and the native email app on smartphones - will train that specific client only.