How are Facebook messages filtered?

[:D]

Sometimes when you send someone a message who you don't know, it goes into their "other" box rather than their "inbox" Do you have to be mutual friends with a person, for the message to go into their inbox? Or what?

[withaC]

,

Via FB:

"If I'm not connected to someone on Facebook, how can I make sure a message reaches their inbox?

Messages you send to someone you're not connected to on Facebook may arrive in their Other folder. You may have the option of paying to route these messages to their inbox. When this delivery option is available, you'll see the price beneath your message.

Because we limit the number of messages a person can receive in their inbox from people they're not connected to, you may not always have this delivery option."