If you don't complete a draft for one reason
or another, and if the draft buffer is no longer available, you
can pick your draft up again with e
(mh-edit-again). If you don't use a draft folder,
your last draft file will
be used. If you use draft folders, you'll need to visit the draft
folder with F v drafts <RET>, use n
to move to the appropriate message, and then use e to
prepare the message for editing.
The e command can also be used to take messages that were sent to you and to send them to more people.
Don't use e to re-edit a message
from a Mailer-Daemon who complained that your mail wasn't
posted for some reason or another. In this case, use E
(mh-extract-rejected-mail) to prepare the message
for editing by removing the Mailer-Daemon envelope and
unneeded header fields. Fix whatever addressing problem you had,
and send the message again with C-c C-c.