Bounced Emails

Emails that could not be delivered. Hard bounces are permanent, soft bounces are temporary.

What are Bounced Emails?

Bounced emails are messages that couldn’t be delivered to the recipient’s inbox. They’re categorized as either hard bounces (permanent issues, like an invalid address) or soft bounces (temporary issues, like a full inbox).

Why it matters

Bounces directly affect your Bounce Rate and, by extension, your sender reputation. High bounce rates tell mailbox providers that you’re not managing your list properly, which can lead to lower Inbox Placement or outright blocking.

How it works

When delivery fails, the receiving server sends back an SMTP error code. AutoSend categorizes these into hard or soft bounces. Hard bounces are added to the Suppression List immediately. Soft bounces may be retried for a period (e.g., 72 hours) before being marked as undeliverable.

Examples

Hard bounce: “550 User does not exist.”
Soft bounce: “452 Mailbox full, try again later.”
Soft bounce: “421 Server temporarily unavailable.”

Best practices

Remove hard bounces from your list immediately.
Retry soft bounces intelligently—don’t hammer the server with repeated attempts.
Use List Hygiene practices to prevent future bounces.

FAQs

What’s the difference between hard and soft bounces?
Hard bounces are permanent and must be removed from your list. Soft bounces are temporary and may succeed if retried. For example, a full inbox might accept your email later once space is cleared.

How many soft bounces are acceptable before removing an address?
It depends on your ESP, but typically after 3–5 failed attempts over a few days, the address should be suppressed to protect your reputation.

Can bounce rates affect my entire domain?
Yes. If ISPs see too many bounces from your domain, they may lower your reputation, affecting all your campaigns—not just the one with issues.