The server cannot deliver your email because the recipient’s inbox is full. Most email applications have a set amount of storage an individual user can use for emails. If this quota is exceeded, the server will not let any more mail through. It also alerts the mailbox owner to do something about it.
We treat this as a soft bounce if it is temporary, but we convert it to a hard bounce if the issue continues.
|Note: This error can also be a sign of an abandoned mailbox.
For example, someone might have set up a free webmail account just for shopping-related emails, then stops signing in if they have moved to a different location.
To know more about Email Bounces and Error Codes, click here