[Dovecot] MAILDIR environment

from docs/mail-storages.txt:

"Also as a special case, if MAILDIR environment exists, maildir storage is used with the directory specified in it."

Forgive me if this seems obvious, but is this talking about setting MAILDIR as an enivornment variable? I have it set on my system in both /etc/profile and ~/.bash_profile:

MAILDIR=/path/to/maildir/ export MAILDIR

and have confirmed this worked by running 'echo $MAILDIR'. I've logged the user in question out and then in again, as well as restarting dovecot but it still defaults to checking ~/Maildir when the user logs in. Setting the location using default_mail_env is not an option here as I need the fallback behaviour that occurs when default_mail_env is not set.

Any advice appreciated.