List hygiene: the six-rule policy

Cleanup is reactive. You notice bounce rates climbing and go hunting for the problem. Policy is preventative — automatic rules that keep the list healthy without anyone having to remember. The six rules below can be encoded as Braze segments or event-based automations. Each one maps to a specific degradation pattern, and each one should run continuously rather than as a quarterly chore.

How often should you run list hygiene? Continuously. The six rules below are automatic segments and event triggers, not a monthly cleanup job. The only quarterly check is auditing that the rules are still firing as intended, which the lifecycle audit checklist covers.

The Deliverability Management skill covers the reputation mechanics these rules protect. Each rule is optimising one of those mechanics directly.

A hard bounce has told you the address doesn't exist, has been disabled, or has an irreversible delivery problem. Send again and you produce another bounce, another negative reputation signal, zero chance of a response. The maths is never close.

The rule: on any hard bounce, move the user's email subscription to permanently unsubscribed from marketing, and flag the profile so manual re-subscription requires verification. Do not send marketing mail to the address ever again.

Transactional can continue (password resets, security alerts) so the user can recover their account if they need to. Anything marketing-flavoured is suppressed permanently. This is one of the few places where "one strike and you're out" is the right policy — because the strike is a fact, not a judgment.

Soft bounces are recoverable in principle — full mailbox, server hiccup. In practice, three in a row usually means the mailbox is abandoned or the provider is treating your mail as spam-adjacent. Continuing past that is a reputation drain with no conversion upside.

The rule: three consecutive soft bounces flags the user for suppression from marketing sends. Re-evaluate if the user engages — opens, clicks, visits the product — within 30 days. Otherwise confirm the suppression permanently.

180 days is the default floor. Aggressive programs sunset at 90; conservative programs at 365. The right threshold reflects your natural engagement cadence — a weekly product can sunset at 90 days, a quarterly product needs 365+. Pick the number that matches how real humans use the product, not an arbitrary round.

The rule: users with no engagement signal (opens, clicks, product visits, transactions) in 180 days move to a "quiet list" that receives at most one re-engagement message per quarter. If they engage, back to active. If they don't respond after two re-engagement messages, permanent sunset.

Expect the list to shrink 5–15% on first implementation for programs that haven't run hygiene before. That's the dead weight. Engagement rate, deliverability, and revenue-per-send all improve as a result. A smaller engaged list outperforms a larger unengaged one on every metric except raw size, and raw size isn't a metric — it's a vanity number that correlates negatively with sender reputation past a certain point.

The win-back flows guide covers the re-engagement sequences that run before final sunset — the safety net that catches users who would have come back if asked.

A user marking an email as spam is the single strongest negative signal in deliverability. Everything else — bounces, unsubs, low opens — is a rounding error next to a complaint. Continue sending after one and the next complaint compounds the reputation damage. Mailbox providers will downgrade your sender reputation quickly if complaint rates climb.

The rule: on any complaint (via feedback loop from major ISPs), suppress the user from marketing and transactional sends immediately. Don't re-evaluate. Don't ask them to re-subscribe. They've told you they don't want your mail; continuing is at best bad manners and at worst a regulatory problem.

Can suppressed users re-subscribe? For 180-day sunsets, yes — automatically on any engagement signal within the grace period. For hard bounces, spam complaints, and traps, re-subscription requires a manual verification step, usually double-opt-in. The friction is intentional. These are permanent suppression triggers for good reason.

Role accounts (info@, sales@, support@) are usually monitored by multiple people, rarely opted in by the role-owner intentionally, and a known source of complaints. Some mailbox providers treat heavy volume to role accounts as a reputation signal — and not a good one.

The rule: role accounts are suppressed from marketing sends by default. They continue to receive transactional. If a specific role account has been explicitly subscribed by an authorised user, flag it for inclusion — but make explicit opt-in the requirement, not the absence of objection.

Spam traps are email addresses owned by mailbox providers or anti-spam organisations that exist specifically to catch senders acquiring list data through dubious means — scraping, purchased lists, old imports, forgotten sign-up forms on domains that now redirect. Landing mail in a spam trap is a major negative signal, and it's usually the tip of a larger iceberg.

The rule: if a third-party deliverability service flags a spam trap in your list (or a pattern suggests one), immediately investigate the source of the address and remove it. Then review the acquisition path — you likely have other similar addresses you haven't identified. Never knowingly send to an address you can't trace to a real opt-in.

How do you identify spam traps proactively? Third-party deliverability services (Validity, Email on Acid, etc.) run trap monitoring. Signs you might have traps without a service: sudden deliverability drops, specific ISPs blocking you, or patterns of addresses that never open, never click, and have suspicious domains. Audit the acquisition path behind anything suspicious. Almost always the trap got in through a channel that skipped consent confirmation.

Each rule becomes a Braze segment or a Braze-managed attribute flag. Hard bounce → excluded from all marketing. Soft-bounce-thrice → excluded. 180-day dormant → excluded from broadcasts, included in re-engagement only. Complaint → excluded permanently. Role-account → excluded by default. Spam trap → excluded and flagged for investigation.

The policy is only useful if it's enforced automatically. Document the six rules. Implement the six segments. Audit quarterly that each is still firing as intended. That's the whole job. The teams that skip the documentation end up with rules that drift — someone loosens a threshold for a specific campaign, nobody tightens it back, six months later the policy exists on paper but not in production.