Types of Hard and Soft Bounces

In the last post, we told you what hard and soft bounces are, this post will help you know their different types.

General Bounce (GB)	If the bounce message is unclear and the email server is not able to deliver the email message, it is treated as soft bounces. Example: "Subject: Undeliverable mail"
General Soft Bounce - (SB)	Email is not delivered to the recipient email address temporarily by the email server. Example: "Connection timed out."
Soft Bounce - Dns Failure (SBDF)	Email is not delivered to the recipient email address due to a DNS problem. Example: "Host is unreachable"
Soft Bounce - Mailbox Full (SBMF)	Email is not delivered to the recipient email address as the recipient's email box is full. Example: "Mailbox over quota"
Soft Bounce - Message Size Too Large (SBMS)	Email is not delivered to the recipient email address because the message size is too large. Example: "Exceeded maximum inbound message size"
Transient Bounce (TB)	Email is not delivered to the recipient email address temporarily, but it is still trying. Example: "Warning: message still undelivered after 4 hours. We will keep trying until message is 2 days old"
Mail Block - Attachment Detected (MBAD)	In this case, the recipient's email server is blocking your email due to an attachment. Example: "552 Disapproved attachment"
Mail Block - Relay Denied (MBRD)	This message indicates that the recipient's email server is blocking the email send by the sender’s email server. Example: "551 relaying denied"
Non Bounce (NB)	This clarifies that the message could be a reply from the recipient and was not a bounce, or maybe an unknown bounce format.
Mail Block - General (MB)	This message indicates that the recipient's email server is blocking the email send by the sender’s email server. Example: "550 Message REFUSED by peer"
Mail Block - Known Spammer (MBKS)	Indicates that the recipient's email server believes you are a spammer and is therefore blocking your email. Example: "REJECT Known SPAM source"
Mail Block - Spam Detected (MBSD)	Indicates that for the recipient's email server the message content appears like spam and is therefore blocking your email. Example: "550 Possible spam detected"

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All you Need to Know About Soft Bounce

Bounce or bounce-back, is a term associated with an email returned back to the sender after being rejected for delivery due to some reasons. The reason for bounce-back can be made out from the description provided in the bounce type itself.

There are two types of bounces, Hard Bounce and Soft Bounce. In case of hard bounce, an email remains permanently undeliverable, due to the reasons mentioned in the previous post. However, in case of soft bounce, it’s a temporary problem where the message gets bounced due to unavailability of the email server or inbox being full.

In soft bounce, the sender’s email reaches the mail server and the mailing address is also recognized by the recipient’s mail server, yet the mail is bounced back undelivered before reaching the recipient. There are many reasons due to which, an email may be soft bounced:

• Server is down
• Mail server is swamped with messages
• Recipient's mailbox is full
• User has abandoned the mailbox
• Message is too large

In most cases, a soft bounce message may be redirected manually to the recipient's domain by the network administrator or delivered at another time. Generally, an attempt is made to deliver the email regularly for a few days as the email address is valid, however, if even after several attempts it remains undelivered, it becomes a soft bounce.

There are different types of hard and soft bounces, which will be explained in the next post.