PowerMTA Bounce Processing & Suppression
Bounces are inevitable — how you handle them decides your reputation. Here's how PowerMTA classifies and processes bounces, and why suppression matters.
TL;DR
PowerMTA auto-classifies hard vs soft bounces and processes feedback-loop complaints. Feeding these into suppression lists keeps your bounce rate low and protects deliverability.
Hard vs soft bounces
- Hard bounce: permanent failure — the address doesn't exist. Suppress immediately and never retry.
- Soft bounce: temporary failure — mailbox full, server down, throttled. Retry on a schedule.
Confusing the two is dangerous: retrying hard bounces repeatedly signals a dirty list and hurts deliverability.
How PowerMTA processes bounces
PowerMTA reads the SMTP response and DSN codes to categorise each failure, logs it, and can route the data to a bounce-handling pipeline. This automation is a big reason it beats Postfix at scale.
Feedback loops (FBLs)
When a recipient clicks "report spam," participating providers send a complaint via a feedback loop. PowerMTA can process these automatically so complainers are suppressed. Register for FBLs and Google Postmaster Tools to see complaint data.
Suppression lists
A suppression list is your do-not-send list: hard bounces, complainers and unsubscribes. Honouring it is both a deliverability and a compliance requirement under Gmail and Yahoo's sender rules.
Keeping bounce rate healthy
Aim to keep hard bounces under ~2%. High bounce rates trigger throttling and blocks. Combine bounce processing with list hygiene for best results.
AutoPMTA surfaces bounces, complaints and suppression in one dashboard so nothing slips through. See pricing.
Key takeaways
- Suppress hard bounces immediately; retry soft bounces.
- PowerMTA classifies bounces from SMTP/DSN codes automatically.
- Process feedback loops to suppress complainers.
- Keep hard bounce rate under ~2% to protect reputation.
Frequently asked questions
What is the difference between a hard and soft bounce?+
A hard bounce is a permanent failure (the address doesn't exist) and should be suppressed immediately. A soft bounce is a temporary failure (mailbox full, server down) that can be retried later.
What is an email suppression list?+
A suppression list is a do-not-send list containing hard bounces, spam complainers and unsubscribes. Honouring it protects deliverability and is required by Gmail and Yahoo sender rules.
What is a feedback loop (FBL)?+
A feedback loop is a service where mailbox providers forward 'report spam' complaints back to the sender, so complaining recipients can be identified and suppressed.