...

## Quota limits

plugin {
  quota = dict:%u::proxy::quota
  quota_rule = *:storage=10M:messages=1000
}

...

## Quota warning
plugin {
  quota_warning = storage=99%% quota-warning 99 %u
  quota_warning2 = storage=97%% quota-warning 97 %u
  quota_warning3 = storage=95%% quota-warning 95 %u
  quota_warning4 = storage=90%% quota-warning 90 %u
  quota_warning5 = storage=85%% quota-warning 85 %u
  quota_warning6 = storage=80%% quota-warning 80 %u
  quota_warning7 = storage=75%% quota-warning 75 %u
}

 ...

## quota warning service
service quota-warning {
  executable = script /usr/local/bin/quota-warning.sh
  user = vmail
  unix_listener quota-warning {
  user = vmail
  }
}

 ...