Help ensure your emails
hit the inbox
Stop guessing why your messages end up in spam. Follow this 26-point checklist to achieve technical compliance, enhanced sender reputation, and delivery success.
Bounces
When an email generates a failure notice (bounce), it’s important to determine whether the cause is hard (permanent) or soft (temporary).
Hard bounces (for example, non-existent addresses) indicate permanent delivery failures. These addresses should be removed from your mailing list immediately. Hard bounces should typically account for no more than 0.5–1% of your total send volume.
Soft bounces (such as full mailboxes, temporary server issues) are usually transient and may resolve without intervention. However, if an address continues to generate soft bounces across multiple campaigns, it should be flagged for review and eventually suppressed. Soft bounces should generally remain below 2–3% of your send volume.
Continuing to send mail to invalid or unresponsive addresses increases costs, degrades list quality, and can negatively impact sender reputation. Mailbox providers monitor delivery attempts to problematic addresses, and sustained issues may result in throttling, filtering, or outright blocking. As a best practice, aim to keep your overall bounce rate (hard + soft) below 2%, with 0–1% being ideal for maintaining a strong sending reputation.