A function called to save outgoing articles. This function will be called with the name of the file to store the article in. The default function is message-output which saves in Unix mailbox format.

When sending combined messages, this string is inserted at the start of the mailed copy. If the string contains the format spec `%s', the newsgroups the article has been posted to will be inserted there. If this variable is nil, no such courtesy message will be added. The default value is `"The following message is a courtesy copy of an article\nthat has been posted to %s as well.\n\n"'.