For bounced emails, what is the difference between a hard and soft bounce?

A 'bounce' means that your email was sent to a specific address, but the mail server that received the email for that person has sent it back, saying it could not be delivered.

There are quite a few different reasons that might happen, and we can divide them into two main categories:

Soft bounce

A soft bounce is an email message that gets as far as the recipient's mail server (it recognizes the address) but is bounced back undelivered before it gets to the intended recipient. A soft bounce might occur because the recipient's mailbox is full, the server is down or swamped with messages, or the message is too large.

If an email has soft bounced in the last 5 campaigns without any trackable activity like an open or a click (and if those 5 campaigns took place over more than 2 days) it will automatically be converted to a hard bounce and be removed from your list.

Hard bounce

A hard bounce is an email message that has been returned to the sender and is permanently undeliverable. Causes include invalid addresses (domain name doesn't exist, typos, changed address, etc.) or the email recipient's mail server has blocked your server.

Servers can sometimes interpret bounces differently, meaning a soft bounce on one server may be classified as a hard bounce on another.

Our email sending application automatically moves subscribers that hard bounce into a "Bounced Subscribers" category, so they don't receive future campaigns.

Tips for reducing bounces

As well as using the built-in bounce handling features, here are some quick tips on ways you can reduce bounces even further:

  1. Keep your subscriber lists clean:
    We will automatically remove invalid email addresses as you add them, but when new subscribers sign up via a subscribe form, they may enter the wrong address. Check each list for incorrectly formatted addresses, invalid domains and typos.
     
  2. Use double opt-in:
    When creating a subscriber list, set it as double opt-in, allowing each address to be validated by the subscriber before it can be added to your list.
     
  3. Monitor Delivery Rates By Domain:
    Track your open and bounces rates by major domain, such as AOL, Hotmail, Yahoo, Earthlink and others. If one is significantly different than the others, or you experience a sudden change, your campaign may be getting caught by spam filters.
     
  4. Test Your Emails:
    Prior to sending your campaign to your entire list, send a test to yourself and others. Make sure you try and include all the major types of email clients used by members of your list when testing.