How to get mutt to use mail aliases

[mdevin@ozemail.com.au]

I have set up a .mail_aliases file for mutt that looks like:
alias mdevin mdevin@ozemail.com.au

In my .muttrc I have:
set alias_file=$HOME/.mail_aliases
source $HOME/.mail_aliases
set edit_hdrs

Now when I try and edit the To: Cc: Bcc: fields and press tab, mutt will
not give me a list of email addresses from my file.  It just tabs across
the screen like tab normally does.

Note: I have gotten it working if I don't set edit_hdrs and get prompted
for the To: address and then press tab.  But the documentation seems to
suggest that it can be done as this quote points out:
"To use aliases, you merely use the alias at any place in mutt where mutt
prompts for addresses, such as the To: or CC: prompt. You can also enter
aliases in your editor at the appropirate headers if you have the
$edit_hdrs variable set."

How do you get mutt to do this or can it only be done with edit_hdrs set
to no?  Do I need to bind the tab key somehow?

Also, I haven't figured out yet how to send mail to another mailbox from
within mutt.  Say you use procmail to filter the debian-user mail into
its own separate file and then read it with mutt.  Then, say you want to
transfer a message you like into your debian-tips file.  How would you
do this?

Thanks to all those mutt users.

Mark.