The step-up's failure count was keyed on the cookie slot, which the
client chooses, so a session could spread guesses over 50 slots; and
even one key allowed 480 failures a day, well above Stalwart's ban of
100 a day per address, which would ban the webmail's own IP for every
user. Failures now count per server and login name, 5 per 15 minutes
and 20 a day.
Linus Rath
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