Failures

Messages of the _fail method family inform the sender of a problem on the recipient's side. A failure is the inability to accomplish a task (a request or other) on the side of the source issuing the _fail.

A classic example would be _fail_filter_strangers indicating that your message cannot be delivered to the recipient as she has denied reception of messages from strangers.

Standard derivate families of _fail are:

• _fail_deliver – could not deliver to destination.
• _fail_necessary – something needs to be provided on recipient's side.
• _fail_redirect – could not accomplish request because something has moved elsewhere.
• _fail_unavailable – something is not available although it should be.
• _fail_unsupported – something is not implemented although it should be.