mh-scan-rcpt-regexp

mh-scan-rcpt-regexp is a variable defined in `mh-scan.el'.
Its value is

"\\(To:\\)\\(..............\\)"

Documentation:
This regular expression specifies the recipient in messages you sent.

Note that the default setting of `mh-folder-font-lock-keywords'
expects this expression to contain two parenthesized expressions.
The first is expected to match the "To:" that the default scan
format file generates. The second is expected to match the
recipient's name as in the default of
"\\(To:\\)\\(..............\\)". If this regular
expression is not correct, the "To:" string will not be
highlighted with the face `mh-folder-to' and the recipient will
not be highlighted with the face `mh-folder-address'