Why does Email Bounce?

With ubiquity in Email Marketing, email marketers are still struggling to figure out the reason behind email bounce. When an email gets rejected by subscriber’s email server, then it is called Email Bounce. When this happens, the mailer will receive an automatic notification of delivery-failure. There are two types of Bounce: Soft Bounce and Hard Bounce. The details of your email bounce rate can be seen in your campaign report. It is better to keep an eye on the bounce rate to make your campaign successful.

Hard bounce stipulates that the email is not delivered due to some permanent reasons. There are several factors for the reason behind hard bouncing of emails, but the supreme reason is permanent failure of email address. The email service providers must remove these hard bounce addresses from their email list immediately to avoid interference with sender reputation.
Reasons behind HARD BOUNCE :

  1.     No Mailbox
  2.     Syntax error

The email addresses which are valid and reaches the email server mail box and bounces back due to some temporary reasons which may include mailbox full are Soft bounces. If an email address continues to soft bounce after every campaign, then it becomes a hard bounce and as I mentioned above, email addresses with hard bounce must be removed from your email list.
Although, it is difficult to find out the reason behind soft bounce, some of them can be encountered as:
Reasons Behind Soft Bounce:

  1.     Error in processing
  2.     Mailbox full(Over quota)
  3.     Mail system full
  4.     Network Congestion
  5.     Mailbox disabled
  6.     Too many recipients
  7.     Service not available
  8.     Undefined mailbox status
  9.     Message size is too big
  10.     Server busy
  11.     Too much spammy content
  12.     IP reputation issue

Besides these reasons, there are more reasons to soft bounce, infact, some cannot be tracked.
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