Notice the difference between a _failure, a _warning and an _error (or several other method families):

Failures

Messages of the _failure 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 _failure.

A classic example would be _failure_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 _failure are:

• _failure_deliver – could not deliver to destination.
• _failure_necessary – something needs to be provided on recipient's side.
• _failure_redirect – could not accomplish request because something has moved elsewhere.
• _failure_unavailable – something is not available although it should be.
• _failure_unsupported – something is not implemented although it should be.

Other example: _failure_unsupported_execute indicates that a _request_execute for CTCP-like interaction with an other person's client has been understood, but fails to produce useful results because that person's client does not provide the requested function. Gotcha: You might also see this message when you have linked an identification, then forgot to set =_source_identification on your subsequent messages.

See also: _failure_redirect.