1 Process message/delivery-status and text/rfc822-headers subparts.
7 Never decode subparts of multipart/encrypted and multipart/signed messages but
8 allow processing of headers of the top-level part, ignoring the top-level part
9 with -I, aborting it with -e or saving the part or subparts with --save-*.
12 Convert dates to the current locale and timezone (with an option?)
15 Allow -d and -p accept shell-like patterns and/or regular expressions:
16 -d content-*,-content-*-encoding
19 Add option --save-as='%format' to generate names for --save-* files. Develop
20 a DSL to conditionally use values of headers, parameters and the counter.