Bounce Back

When an email is unable to be delivered to the recipient, a bounce back email will be received by the sender. This bounce back email usually contains a brief explanation about the failure and a copy of the original email.

There are 6 types of bounce back emails in our system: (Definition of Hard/Soft Bounce)

Hard Bounce Soft Bounce
1. Non-Existent Address 3. Mailbox Full
2. Undeliverable 4. Vacation/Auto Reply
  5. Blocked
  6. Other

1. Non-Existent Address

This is the most common type of bounce back. Sender receives it when a recipient is not found.

Exceptional Case:

Owing to the abuse of spam mails recently, recipients tend to use fake "non-existent address" bounce back to fool spammers.

How to handle?

Our system will not delete your contacts even it is bounce back. You can observe those email addresses one to two times before you remove them.

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2. Undeliverable

Different from "non-existent address", "undeliverable" means the server specified in the email doesn't exist. For example, abc@yahoo.google.com, is an undeliverable address because we can't find a server called "yahoo.google.com".

Exceptional Case:

The recipient's server may be temporary unavailable or under maintenance. If you send emails during this period, you will receive an "undeliverable" bounce back email.

How to handle?

Our system will not delete your contacts even it is un-reachable. It is less serious that "non-existent address", you can observe those contacts one to two times before you remove them.

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3. Mailbox Full

This is the second common type of bounce back. It is sent when the recipient's mailbox is full.

How to handle?

It is not a big problem. You may leave it and resend later on.

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4. Vacation/Auto Reply

This bounce back happens when your recipient is not in office and auto-reply is set for incoming emails.

How to handle?

It is not a problem. You may leave it because the recipient will receive the email once the mailbox is capable of accepting emails.

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5. Blocked

When an email contains prohibited or spam-like content, this bounce back will be sent. The target of blocking can be certain images, links, brand names or even a particular phrase. The rule of blocking is to not open to public and it keeps changing.

It is not easy to tell which word causes blocking or which one avoids. By the way, when you find a lot of "blocked" emails, you should revise the content of your email.

How to handle?

Other than revising the content of your emails. You may try to contact your recipients and ask them to click a "Not Spam" button to keep your emails away from spam-filters. It is the most effective way to avoid blocking.

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6. Other

When we are unable to recognize the bounce back email or the bounce back email can't be classified into those standard bounce types, they will appear in this category.

How to handle?

Most of the time, they are temporary issues and you don't need to worry.

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