Email bounce management | Online Help - Zoho CRM

Email bounce management

A bounce warning indicates that one or more of your emails have been rejected by the recipient's email server. This can be caused by a variety of factors, including an invalid email address, a full mailbox, or a blocked domain. It's important to understand the cause of the bounce and take steps to prevent it from happening again. This may include updating your contact list to remove invalid email addresses, ensuring that your emails are not marked as spam, and avoiding sending too many emails in a short period of time. Additionally, Zoho CRM provides tools to help you monitor your bounce rate and take corrective action. With these tools, you can quickly identify and address any issues that may be causing your emails to bounce.
Watching out for a high bounce rate   
The "Bounce rate" refers to the percentage of email recipients who did not receive the emails you sent to them. Although a small number of bounces are to be expected in bulk emailing, a warning will be issued when the bounce rate crosses a certain limit. To set a benchmark, a bounce rate under 5% in Zoho CRM is acceptable. Anything more than that needs to be attended to immediately.
Read further to learn more about how you can avoid email bounces.

Avoiding email bounces 

Your emails can bounce for multiple reasons. Depending on the reason, bounces can be broadly classified into hard bounces and soft bounces.
  1. Email addresses are classified as hard bounces when Zoho CRM determines that emails cannot be delivered permanently to those addresses. Consequently, these email addresses will be blocked, preventing any future email from Zoho CRM.
  2. Email addresses are classified as soft bounces when Zoho CRM determines that emails cannot be temporarily delivered to those addresses.
In Zoho CRM, email bounces are divided into two types: Temporary and Permanent. Temporary bounces include soft bounces and certain types of hard bounces. If an email address is temporarily blocked, you can unblock it directly. However, hard bounces are usually permanent and cannot be unblocked within CRM.

If you believe that a permanently bounced email address is now deliverable, you can seek assistance from our support team at with relevant details and we will take necessary measures to whitelist Zoho CRM.

Checking details for bounced email addresses

You can find the details of the bounce type and category for email addresses that bounced in the following sections of your CRM:
  1. Record Details page
    If an email address in the record details page bounces, a warning icon will be displayed. Hover over the warning icon to view the details regarding the bounce category.

  2. Email Related list
    If an email is unable to be delivered, the email related list will display its status along with information about the type of bounce.

  3. Module view/List view
    When you apply the filter to the blocked email field on the module view/list view page of records, you will see similar warning icons for the different bounce types. 

Understanding the different types and categories of bounce 

The following table presents various bounce warning messages that may be encountered for blocked email addresses. Before resolving bounced emails, we advise that you review the suggested approaches for temporary and permanent bounces.

Soft bounces and Temporary Hard bounce Categories

Temporary Domain Failure

Unable to find the domain connected to this email address.
Some reasons for not being able to find a domain are if the domain's registration has expired or been discontinued, the DNS records of the domain are incomplete, or the domain name is misspelt in the email address. To resolve this issue, we recommend that you ensure that the email domain is valid, then contact the recipient by other modes of communication to check the status of their domain.

Out of Office
The recipient is not available to check their emails or on vacation.
When the recipient has configured an 'out of office' setting in their mailbox, you will receive an automatic bounce message, mentioning their absence. We recommend that you either wait until the recipient is available again or contact some other person mentioned in their auto-reply for further questions.
Authentication failure
The email has bounced or is blocked due to the policy restrictions of the recipient's server, or your email relay servers.
When you have not authenticated your email-sending domains in Zoho CRM via SPF, DKIM protocols, or both, any emails you send using non-authenticated domains could bounce due to policy-related reasons. This issue could also occur when the email policy set by your recipient's organization rejects your IPs or domains. Please ensure that you have completed the authentication of your domains inside Zoho CRM, or reach out to your recipients and ask them to check their policy statuses, and preferably to whitelist the sender IPs used by your account to send emails (both the default Zoho CRM IP addresses mentioned in the next section, and your IP addresses if your organization has set up email relay servers).
Mailbox full
The recipient's mailbox has reached its storage limit.
When the recipient's mailbox has reached its storage limit or is very close to doing so, or when the recipient receives emails with large attachments that their email provider does not support, your emails could bounce back citing 'Mailbox full'. We recommend that you contact the recipient and ask them to free up some storage. You can also verify if the emails you have sent to them contain any large attachments that you could do without.

Temporary Network Error
Your email relay server has failed to send the email to the intended mailbox.
Relaying refers to the process of transferring emails from one mail server to another to deliver them to the recipient. If there are any issues while performing this action via email relay servers you have set up within Zoho CRM, then the email could bounce citing 'Temporary network error' as the reason. We recommend that you troubleshoot your configured email relay server, and also reach out to the recipient to ask if their email providers, domains, or internal systems have recently gone through any major changes or disruptions.

Content related
This email has been marked as spam by the recipient's email server.
When an email has been flagged manually as spam by your recipient, or if it is automatically being filtered out by the spam filters of your recipient's server, then those emails could bounce citing 'Content related' as the reason. We recommend that you check your email for reasons why it could have been marked as spam. This includes the content you send, the URLs in your email, the type of attachments you are trying to send, and so on. Also, ensure that you have authenticated the domains connected to your email addresses, via SPF, DKIM, or both via Zoho CRM, to reduce the possibility of your emails landing in spam.

The recipient's mailbox is not reachable due to unknown reasons.
When an email bounce reason does not fall into any of the above-listed categories, it will be marked as 'Others'. One of the possible solutions is to ask your recipient's organization to whitelist the IP addresses your Zoho CRM account uses to send emails. This includes the default IP addresses, as shown in the section below, but could also include your IP addresses if you have set up email relay servers.
We recommend that you resolve the issue with your recipients before unblocking them inside Zoho CRM for future email sending. Continue monitoring mail sent to them to avoid future blocks which will also have an impact on your deliverability.

Default Zoho CRM IPs







Permanent Hard bounce categories

Sender Denied
Cannot email this address, as your sender domain has been blocked by the recipient.

Bad domain
The recipient's email address contains a domain that doesn't exist or is no longer active.

Bad Mailbox
The recipient's email address does not exist or is no longer active.

Policy related
Unable to email this address due to restrictions by the recipient's server, or by your email relay servers.

Protocol error
Unable to email this address due to technical issues in your emailing protocols and/or SMTP servers.

Relay prohibited
Unable to send emails to this address as the email relay servers you have configured do not recognize you as an authenticated user.

Routing error
Cannot email this address, as the recipient has issues with the configuration of their email server.

Potential spam
This occurs when an email is found to be spam by the recipient's email server.

The recipient's mailbox is not available, or we receive bounce reasons that cannot be explained using the categories listed above.

Unblocking bounced email addresses 

For primary and secondary email addresses that get bounced for temporary reasons, you can unblock them from within your CRM.
You can unblock bounced emails from the following places:
  1. Record details page
  2. Module view/List view
  3. Mass action for unblocking emails
To unblock bounced emails from the Record details page:
  1. Go to the email field for which the email address bounced.
  2. Hover over the info icon for details about the bounce type.
  3. Click Unblock Email Address.

  4. Check the confirmation box that the reason for the block has been resolved.
  5. Click Confirm.
To unblock bounced emails from the list view page:
  1. Go to the module list view.
  2. Apply filters for the blocked emails:
    1. Select Temporary, Permanent, or Both.
    2. You can additionally apply filters for the specific bounce type or filter by any type.

  3. Hover on the warning symbol beside the bounced email and follow the steps as per unblocking bounced emails from the Record details page. 

To unblock bounced emails using mass action:
  1. Select the records to be unblocked.
  2. On the actions button, click Unblock Email Address.

  3. Check the confirmation box after resolving the reason for the bounce.
  4. Click Confirm.
If both the primary and the secondary email addresses are temporarily bounced, you can select whether to unblock the primary email address, the secondary email address, or both during the mass action.

Periodic unblock based on conditions
We have established a periodic review every six months whereby the system will automatically unblock previously blocked email addresses if the issues leading to their blockage have been resolved.
For instance, addresses that were blocked due to policy-related reasons will be reinstated if we can confirm proper email authentication.

Best practices to avoid email bounces

Regardless of the type of email bounce, it is good practice to follow the suggestions mentioned below to continue sending emails from Zoho CRM without hassles.

Avoid formatting issues while importing a list into Zoho CRM   
Often, when you import leads and contacts in Zoho CRM, there may be formatting errors in your import sheet that you have missed. Make sure you check the following points while you import a list:
  1. In your import sheet, find and remove any additional characters in the Email address field, such as commas, quotation marks, spaces, and so on.
  2. Make sure each column is titled correctly, after the respective field names. For example, First Name, Last Name, Email Address, and so on.
Avoid sending emails to old and stale email lists   
One of the most common reasons for email bounces could be that your contact list is outdated.
When we say "stale list", it could mean any of the following:
  1. The email addresses are no longer valid
  2. The contacts have not been getting emails from you for a long period (say more than six months).
  3. Your leads and contacts changed their email address a while back.
  4. Your contacts have not been using their email account for too long, so the account has stopped working and started returning bounces.
  5. The recipient email domains have expired.
In any of these cases, there is a good chance for your emails to bounce. It's good practice to check and update the list of leads and contacts at regular intervals. If it's been too long since you sent a batch of emails, reconfirm your contact list before you send another set of emails.

Avoid using a public domain address as your "From" address   
Your emails are very likely to bounce if you have been using a public webmail address as your "From" address.

Free web domains do have strict policies to avoid spam. However, when you use such an email address to send your emails via Zoho CRM, your emails are very likely to bounce. For example, if you send emails via Zoho CRM using, the receiving servers will identify that the email is not directly from Yahoo, but via another platform. In this case, the servers may reject the emails, resulting in an email bounce.

For this reason, we strongly recommend that you use your own private domain-based email address in Zoho CRM to send mass emails to customers.

Avoid buying email addresses from illegitimate sources   
If the email addresses of your leads and contacts have been collected at different points in time from untrustworthy sources, they are likely fake or invalid. It is better not to send to bought or harvested lists. It is highly recommended that you verify and confirm the interest of your leads and contacts in receiving the emails before you send bulk emails to them.

Remove invalid email address   
To make sure your contact lists do not become obsolete, ensure that you verify the email addresses at regular intervals. Over time, it is likely that some email addresses shutdown due to prolonged inactivity and become invalid. Make sure to delete such invalid email addresses.

To check your email bounces, Zoho CRM offers you an Email Bounce report by default. This report can be accessed from Reports > Email Reports > Bounce Report.

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