Email bounces

Email bounces occur when an email doesn't reach the recipient. As a result, the sending server is shown an error message. Bounces can be due to varying reasons. However, they are largely categorised as hard and soft bounces.

Hard bounce occurs when there is no possibility of your emails being delivered. It can be due to an incorrect recipient email address, fake email ids or some IPs being deliberately blocked by the recipient servers.

Soft bounce on the other hand occurs when there is a temporary rejection. This can be due to the receiving server being temporarily down, the size of the email being large or the recipient's inbox being full. Soft bounce can also be a result of the receiving server temporarily blocking emails from some IPs.

Bounce categorisation  

ZeptoMail categorises the bounce error shown to understand the reason behind them better. The categorisation groups similar errors into a particular category. The following are the bounce categories we use :

  1. Connection issues :This error occurs when the sending server is unable to establish a proper connection with the recipient. Possible reasons can be a misconfiguration of DNS records on the recipient side, temporary unavailability of the recipient server or networking issues on the recipient side.
  2. Policy failure : This error results due to the policies on the recipient side. Some servers can have policies blacklisting emails from certain email addresses or IPs. In such cases, you can contact the recipient asking them to add your IPs, or domains to the trusted list. In some cases, some receiving servers may reject emails when the recipient inbox exceeds the allowable size. Some servers may also bounce emails coming from new domains or IP as a precautionary measure to avoid spams. 
  3. Spam: Errors in this category are usually a result of certain sections of your email being identified as spam. Alternatively, spam errors can also occur due to the sending domain and IP address having a low sender reputation. Transactional emails being flagged as spam is a serious issue that has to be resolved for further email delivery.
  4. User not found: This error is a type of hard bounce where the recipient email Id no longer exists in the recipient server. It can also be due to email addresses being disabled from further usage or an invalid email address. 
  5. Invalid DNS : An invalid DNS error will be shown when the sending server is unable to reach the recipient's IP address. This means that the recipient has not properly configured their DNS to receive emails to their domain. 
  6. Others : The errors in this categories do not fall into a particular group and are unique. 

Accessing the Bounce categories in ZeptoMail :

You can view the Bounce categories in the following sections :

  • Dashboard : The Bounce categories in ZeptoMail can be viewed near the Mail analysis section. This section displays all the bounce errors in your account in a graphical manner.

  • Mail Agent : The overview section in the Mail agent gives a consolidated graph of the different Bounce error categories of emails sent from that particular Mail agent.

  • Processed emails section : The Search criteria filter in the processed emails section allows you to search for emails based on the different bounce errors.


Before you get started it is important to know that ZeptoMail is for sending transactional emails like welcome emailers, password resets emails, OTPs. We do not support sending of bulk emails or promotional emails like newsletters or marketing campaign emails. If you are looking for a bulk email provider, you can visit Zoho Campaigns.