-- ``--chains <directory>``, ``-c <directory>``: directory to load chain configurations from.
-- ``--states <directory>``, ``-s <directory>``: directory to store states in.
+- ``SMTP_HOSTNAME``: the hostname of the SMTP server, is used for error emails; default is “localhost”
+- ``ERROR_EMAIL_SENDER``: the email address to use as sender for error emails
+- ``ERROR_EMAIL_RECIPIENT``: the email address to send error emails to
+- ``CHAIN_DIRECTORY``: directory to load chain configurations from; default is “chains”
+- ``STATE_DIRECTORY``: directory to store states in; default is “states”