rmail-summary-by-regexp
rmail-summary-by-regexp is an interactive autoloaded Lisp function in `rmailsum.el
'.
(rmail-summary-by-regexp REGEXP)
Display a summary of all messages according to regexp REGEXP.
If the regular expression is found in the header of the message
(including in the date and other lines, as well as the subject line),
Emacs will list the message in the summary.