I have now found two Facebook conversations from the end of September 2012 where replies ended up in Facebook's spam filter because I was not friends with the person I was speaking to. It appears that Facebook started treating these as spam on 1st October 2012.
To see what messages you have missed you need to look in your "other" folder.
This is where your "other" (spam) folder is:
- Log into Facebook. Go to the top left of the page.
- Click on the two speech bubbles symbol.
- Under your list of messages there is a link that says "see all".
- Click on this. At the top of the next page you should see Inbox and next to that Other.
- Click on other.
- Now you can click on all the messages that are sitting in there.
This is the quick way to get to it:
Make sure you are logged into facebook and go here to see yours:
https://www.facebook.com/messages/other
You may want to share this information with your friends.
