Hard Bounce vs Soft Bounce: What's the Difference and What to Do About Each

·2 min read

Open any email marketing report and you'll see two labels: hard bounce and soft bounce. They sound similar, but they mean very different things, and treating them the same way costs you.

Hard bounce: a permanent dead end

A hard bounce means the email can't be delivered and never will be. Common reasons:

  • The address doesn't exist.
  • The domain is wrong or no longer in use.
  • The mailbox has been closed.

What to do: stop sending to that address and remove it from your mailing list straight away.

Soft bounce: a temporary problem

A soft bounce means the address is probably real, but something stopped delivery this time. Common reasons:

  • The inbox is full.
  • The receiving server is down or slow.
  • The message was too large.

What to do: try again once or twice over a few days. If it keeps failing, treat it as a hard bounce and remove it.

Quick comparison: hard bounce vs soft bounce

Hard bounce Soft bounce
What it is A permanent dead end A temporary problem
Typical cause The address doesn't exist A full inbox or a server that's down
Permanent? Yes No
What to do Remove it from your mailing list now Retry once or twice, then remove it if it keeps failing

Where do catch-all addresses fit?

Catch-all domains accept mail for any address, so it's impossible to be sure whether a particular mailbox exists. They won't always bounce, but they can turn into hard bounces later. VerifyFlow flags them so you can test them with a small send first.

How to stop hard bounces before they happen

Most hard bounces can be caught before you press send:

  1. Export your mailing list as a CSV or Excel file.
  2. Pay for VerifyFlow, get your access code and upload the file. It's a flat £20 per list, up to 1,000,000 rows.
  3. Remove the invalid addresses.
  4. Keep catch-alls separate and test them.

How to reduce soft bounces

Soft bounces are harder to prevent, but you can keep them low by sending at sensible times, keeping messages light, and removing contacts who keep failing.

Final thoughts

Hard bounces are permanent dead ends you should remove, and soft bounces are temporary problems you should retry. Verify your mailing list with VerifyFlow to catch the first kind early, and your email marketing will run much more smoothly.

Find out who's real before your next send

Verify up to 1,000,000 addresses in one CSV or Excel file for a flat £20. No subscription, no account.

Keep reading

How to Check if an Email Address Exists Without Sending an Email

Need to know if an address is real before you send? Here are quick manual checks, why they fall short, and how to check a whole list at once.

How to Verify a Large Email List (Up to 1 Million Addresses) Without a Subscription

Got a huge mailing list and no appetite for another monthly bill? Here's how bulk email verification works, and how VerifyFlow checks up to 1,000,000 addresses for one flat £20.

How to Verify Emails in an Excel or CSV File: A Step-by-Step Guide

Your mailing list probably already lives in a spreadsheet. Here's a simple, step-by-step way to verify emails in an Excel or CSV file without extra software.