Bounce rate is the percentage of messages in an email campaign that could not be delivered to the recipient's inbox. It is one of the core deliverability metrics: a high bounce rate signals problems with list quality, sender reputation or authentication, and it directly damages how mailbox providers treat your future sends. The formula is simple — bounces divided by total messages sent, multiplied by 100.
How bounce rate works in practice. Bounces split into two categories. A hard bounce is a permanent failure — the address does not exist or the domain is invalid — and should never receive mail again. A soft bounce is temporary — the mailbox is full, the server is offline, or the message was greylisted — and may succeed on retry. Healthy senders aim for a total bounce rate under 2%; anything over 5% is a strong signal that mailbox providers will start blocking your IP and domain.
Why bounce rate matters for senders. Bounce rate is one of the first numbers Gmail, Yahoo and Microsoft look at when deciding whether your campaign reaches the inbox, the spam folder or nothing at all. Keeping it low protects your sender reputation, your engagement metrics and your domain — which is why list hygiene, double opt-in and automatic suppression of hard bounces are non-negotiable for serious email programmes.
Mailpro and bounce rate
Bounces tracked and suppressed automatically
Mailpro monitors every send, sorts hard from soft bounces, and removes permanent failures from your list — so your reputation stays clean and your next campaign reaches the inbox.