How to get mail from $MAIL into Evolution or Thunderburd

[Jonathan Ryshpan]

How do I get either Evolution of Thunderbird to incorporate mail from
the standard unix $MAIL folder, /var/spool/mail/jonrysh?  

Evolution seems to provide a method; it allows incorporation of mail
from a local Unix standard mail file, but won't allow me to name my
actual local folder, giving me the error "File already exists".

Thunderbird seems to only know about POP and IMAP servers; it doesn't
seem to know anything about local mail delivery at all.

Thanks - jon