Introduced property com.openexchange.imap.failedAuthTimeout in file 'imap.properties' to specify how long such a failed authentication is remembered to avoid possible DoS attack. Default value is 10 seconds.
Available with v6.20.5

# The number of milliseconds a failed authentication attempt is cached
# to faster handle subsequent authentication attempts
# Default is 10 seconds.
com.openexchange.imap.failedAuthTimeout=10000