Bounced Emails
Non Delivery Report/Receipt (NDR)

This article describes the subject of Bounced emails, automatic return of the world's various mail servers such as Gmail, Yahoo, Hotmail and AOL alerting the sender that there is a problem to the deliver the email to the recipient.

When an email is sent from a mailbox that belongs to a specific mail server to a mailbox located at another mail server, the receiving mail server has to move the message to the recipient's mailbox or to produce an automatic bounced email message.

Bounced messages divide into 4 main types:

Hard Bounced Emails

Hard bounce emails are difficult related errors refering usually to mailboxes that do not exist. For example - we wanted to send an email to but maid a typo and sent it to instead. Gmail servers will return us a bounce answer that they do not have such a mailbox and therefore the email could not be transferred to the recipient. This is an Hard Bounce and unless we know the recipient personally it would be difficult to fix this email address. Double opt-in mechanism usually avoids hard bounce messages.

Soft Bounced Emails

Soft bounce emails are light related errors usually refering to mailboxes that temporarily can not receive emails. For example an over quota mailbox which will only be active when the user cleans it and deletes emails from it.

Transient Bounced Emails

Transient bounce emails are errors which relate to the email domain name. For example - we wanted to send an email to but made a typo and sent it to Since we made a mistake our mail servers will not deliver the email to Gmail servers but will try to deliver them to servers instead, but there is no such domain and we will receive a transient error message. These messages are relatively easy to fix for some of the email addresses since we can identify the mistake and correct the email address.

Spam Bounced Emails

Spam bounce these emails are spam errors. The mail server we sent the email claimed that we are not allowed to send and email to the specified email address from a certain reason and therefore it recognizes us or the message we sent as a spam email. You can not do much in this case but to check whether the content that you sent to the recipient included spam related content. For example, scripts, problematic words etc. Recommended reading HTML-based newsletter tips.

World mail servers take the bounced messages they produce very seriously and expect the sender not to ignore them. A sender that ignores these messages may be blocked by certain mail servers and will not be to send email to mailboxes hosted on them for a specific period or even get a negative rating which can move the emails he sends them directly to the recipient's spam box.

Also, sometimes there may be a mail server, usually the small one, which will produce a wrong bounce email message and this is why it is important to keep track after the bounce messages over time.

ITnewsletter system performs an automatic bounce messaeg tracking and improves the recipients data in each account. Recipient who has received bounce messages will become inactive according to the bounce rules. For example, two consecutive hard bounce messages deactivate the recipient so we would not send him another email. This also saves newsletter distribution costs as well as mail servers understanding that the sender takes the bounce messages sent to him seriously and his rating goes up.