message-unsent-separator

message-unsent-separator is a variable defined in `message.el'.
Its value is

"^ *---+ +Unsent message follows +---+ *$\\|^ *---+ +Returned message +---+ *$\\|^Start of returned message$\\|^ *---+ +Original message +---+ *$\\|^ *--+ +begin message +--+ *$\\|^ *---+ +Original message follows +---+ *$\\|^ *---+ +Undelivered message follows +---+ *$\\|^------ This is a copy of the message, including all the headers. ------ *$\\|^|? *---+ +Message text follows: +---+ *|?$"

Documentation:
A regexp that matches the separator before the text of a failed message.