Within the newsletter statistics we find, at the bottom, the OUTPUTS list where the percentages of non-deliveries that occurred during the sending of emails are indicated with the codes relating to the response received from the recipient server below.

Below you will find the codes used by the most common mail servers, some codes that appear in the list visible above may be related to custom mail servers.

SOFT BOUNCE: Temporary bounce

A soft bounce occurs when the recipient’s address is valid but the recipient’s server rejects the email, which is then not delivered. Here are some reasons why this happens:

• The recipient’s mail server is unavailable
• The inbox is full (the allotted quota has been exceeded)
• The domain name does not exist
• The email is too big
• The email was blocked due to its content
• Email can’t be forwarded between mail servers
• The email cannot be forwarded for unknown reasons
• the email was blocked due to sender or IP reputation

The soft bounce email was tried to deliver for 36 hours without success.

HARD BOUNCE: Permanent non-delivery

The e-mail is rejected because:

• The recipient’s email address does not exist or is invalid
• The recipient’s mail server has blocked the delivery.

If an address is hard bounced, it is removed from the list of addresses to which emails should be sent.

BANNED
The sender address has been blocked by the server

UNKNOWN
The recipient address is unknown

SPAM
The sender address has been marked as spam

INVALID EMAIL
The recipient address is not formatted correctly

BLOCKED
The sender address has been blocked by the user

Here you can find some best practices to implement to ensure that bounces in your campaigns are minimized.