Initialize IMAP_ENABLED with false

This matches the behavior described in the README.

Author: kajoik

assets/runtime/env-defaults

@@ -99,9 +99,6 @@ IMAP_USER=${IMAP_USER:-${SMTP_USER}}
 IMAP_PASS=${IMAP_PASS:-${SMTP_PASS}}
 IMAP_SSL=${IMAP_SSL:-true}
 IMAP_INTERVAL=${IMAP_INTERVAL:-30}
-if [[ -n ${IMAP_USER} ]]; then
-  IMAP_ENABLED=${IMAP_ENABLED:-true}
-fi
 IMAP_ENABLED=${IMAP_ENABLED:-false}
 
 ## INCOMING MAIL (ADVANCED CONFIGURATION)