Hard and Soft Bounces. Similarities and Differences
Just like a letter to an old friend can not be delivered, if he changed the address, your email can not be delivered to the customer’s inbox, due to a number of reasons. And when an email is rejected by your customer’s email server, you receive a Non-Delivery Report/Receipt (NDR) informing you about a delivery problem. This is called a bounce.
What is a Hard Bounce?
Permanent email delivery failures, occurring, when your customer’s email address is invalid or is no longer in use. For example, the domain name (the bit after the @) no longer exists or it no longer has registered mail servers. Simple typos, such as “gnail” instead of “gmail” will also cause a hard bounce.
These are the main reasons why your emails hard bounce:
- A non-existent email address (the email address could have a typo or the person with the address may have left the organization)
- Undeliverable email (the receiving email server is temporarily unavailable, was overloaded, or couldn’t be found)
- Blocked email (If the email addresses are placed within the “Blocked” category, the receiving server has blocked the incoming email)
- Other (Bounces that don’t give the server a reason for bouncing are put in this category)
What is a Soft Bounce?
Temporary email delivery failures, occurring when the recipient’s mailbox is full; the receiving server is down or swamped with messages; the message size is too large, etc.
- Mailbox full (your contact has so many emails in their inbox that they can’t receive more)
- DNS failure (happens when your customer’s email server is unable to deliver your email due to DNS issues at their end. This may or may not be a temporary problem)
- Vacation/Auto-Reply (someone goes on vacation or can’t check their email)
- Challenge-response error (a message sent by a filtering service installed by a customer to help filter emails from unknown senders and spam emails)
- Other errors (when an ISPs don’t use a standard error message when they send back the bounce response code–we categorize these bounces as “Other”)
It’s easy to ignore the bounce section in your email reports, but if you do, they’ll sooner or later start to pile up. Then you’ve got a problem.
