If you find a message wrongly classified as spam, you can unmark the message.

To do so:

  1. Select the "More" label, located on the right of your email.  It should reveal the "Spam" label.
  2. Select the "Spam" label
  3. Select the message,
  4. Select the Not Spam button that appears at the top of your view.
  5. Unmarking a message as spam will automatically move it to your inbox.
  6. To find the message, select the "Inbox" label. 

If you're still having issues, you can create a filter:

To prevent this problem from persisting for emails from a specific domain, follow the following steps:
       1. Click the little triangle next to the search box at the top of the Gmail window.


       2. Enter "@example.com" in the From box, then click "Create filter with this search"


       3. Check "Never sent it to Spam" and any other filters you'd like


       4. Click "Create Filter".