netfilter-mailcow ships sensible defaults but every public-facing mail server should review them.
UI: Access → Fail2ban tab. Tunables:
| Setting | Default | Recommended |
|---|---|---|
| Max attempts | 5 | 3 |
| Find time (s) | 600 | 600 |
| Ban time (s) | 1800 | 86400 (24 h) |
| Permanent ban after | 5 short bans | 3 |
Rate limit submission (per UI → Configuration → Rate limits):
| Limit | Sane value |
|---|---|
| Per mailbox / hour | 200 |
| Per domain / hour | 2000 |
| Per IP / hour (smtp) | 100 |
Block prevention beats cleanup — once an IP hits a Spamhaus listing, you're delisting for weeks.
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