Miscellaneous Mew config questions

[Sean McAfee]

I recently started using Mew as my mailreader at work.   It seems to be
basically working well, but there are a few issues I haven't been able
to easily resolve by consulting the documentation.

One:  It seems that every person in my company sends HTML-only mail; not
a text/plain multipart/alternative to be had.  I can press "." to render
the content using w3m, as Mew prompts me to do, but I'm having to do
this for virtually every message.  Can this be automated somehow?

Two:  It would seem that Mew can only send mail by talking directly to
an SMTP server, unlike Emacs's built-in mailer, which just pipes it to
sendmail.  I'm not running a local SMTP server, and if I connect to my
company's main server, I need to provide my password.  Can Mew be
configured to send mail by just piping to sendmail?

Three:  How can Mew be apprised of new MIME content handlers?  I've
received an attached audio file that requires special handling to play,
but I don't see how to let Mew know about it.  Mew tells me: "To specify
appropriate Content-Type: and execute an internal/external command, type
C-c C-e."  When I do so, it prompts me for a MIME type from a limited
list; I can't enter a new type.  I tried adding the new type to my
~/.mailcap file, but Mew is none the wiser.  Indeed, a grep through the
Mew source for the string "mailcap" turns up nothing.

Can anyone provide guidance for any of the above issues?  Thanks in
advance for any help.