Your sendlist is where any non-addressed messages go. Many users set their
sendlist to a single discussion, such as "-apricot", since most of their sends
go there anyway.
Keep in mind that anything the server cannot parse is sent to your default
sendlist. For this reason, many users disable their sendlist.
If you have no sendlist, the server will notify you that it could not send your
message, instead of sending it out by default.
(see also: send)