Email Bounces | Online Help - Zoho CRM

Understanding Email Bounces

Sometimes when you send emails from Zoho CRM, you may notice that the mails have bounced and as a result, not delivered to the recipients. Following are some frequently asked questions on what bounces are and how you can overcome them.

What are bounces?

Bounces are those email addresses to which Zoho CRM could not deliver your email. There may be many reasons why this happens. Based on these reasons, bounces are largely classified as hard bounces and soft bounces.

Email addresses are marked as hard bounces, when Zoho CRM finds that emails are permanently undeliverable to those email addresses. In such a case these hard bounced email addresses will be blocked. This means you will not be able to send any mails to them from Zoho CRM again.

Email addresses are marked as soft bounces when Zoho CRM finds that emails cannot be delivered only temporarily to those email addresses. In such a case, you will be allowed to send a mail to the soft bounced email address five more consecutive times. If at the end of the fifth time, the mail is not deliverable, it will be considered as hard bounce and the email address will be blocked.

Why has my email bounced?

Following are the most common reasons why your email may have bounced.

  • The recipient email address is invalid
  • The mail server of the recipient email address is down.
  • The recipient's inbox is full.
  • The recipient domain name does not exist.
  • Your email has been repeatedly marked as spam by the recipient.

What is a hard bounce?

A hard bounce is that email address to which an email is permanently undeliverable by Zoho CRM for different reasons. A few of them are:

  • The recipient email address does not exist.
  • Domain name does not exist.
  • The mail server of the recipient has completely blocked delivery.

When an email has hard bounced, it will be blocked by Zoho CRM permanently.

What is a soft bounce?

A soft bounce is that email address to which an email is temporarily undeliverable by Zoho CRM for various reasons. A few of them are:

  • Your email is too large.
  • Recipient's inbox is full.
  • The recipient's server is down or offline.

When an email has soft bounced, you will still be allowed to send further emails upto five times. If at the end of the fifth consecutive time, Zoho CRM is not able to deliver the email, the soft bounce gets converted as a hard bounce and so the email address will be blocked permanently.

Will soft bounced email addresses be blocked permanently?

If an email address has been marked as soft bounced, you will be able to send the email to the recipient five more times. If at the end of the fifth consecutive attempt, the mail delivery fails, then it will be marked as hard bounced and further emails to this email address will not be allowed.

My email to a valid email address has been marked as hard bounced. Why?

If your email to a valid email address has been marked as hard bounced, it may be largely because Zoho CRM has been blocked by spam filters or recipient firewall. This happens in two cases:

  • Spam filters have detected your emails as spam.
    Sometimes spam filters such as Spamhaus may detect your email content as spam and block Zoho CRM. This will not only affect your future emails, but also that of other Zoho CRM customers. In such a case, it is good to adopt clean email marketing practices so that your emails get through the spam filters. Some common guidelines are as follows:
    • Keep the email relevant to the recipient.
    • Do not send emails that are too large.
    • Do not include objectionable media in the email content.
    • Do not send too many emails at once.
    • Make sure that the Email subject line is relevant to the content of the email and does not mislead the recipient.
  • Spam filters have NOT detected your emails as spam, yet, they have bounced. 
    Sometimes, due to no fault of yours, your emails to a valid email address may bounce. This is because, Zoho CRM may have been blocked by spam filters and recipient mail servers due to exploitation by other users. In such a case, please write to Zoho CRM Support at with relevant details and we will take necessary measures to whitelist Zoho CRM. Alternatively, you can also directly write a request to the recipient IT admin to whitelist Zoho CRM.

Can I unblock a hard-bounced email address?

If you are convinced that the email address is valid, you can request Zoho CRM Support at to check and unblock a hard-bounced email address.

What if Zoho CRM is blocked?

If Zoho CRM is blocked, we will immediately take the necessary steps to whitelist our IP address. In case your email has bounced because Zoho CRM is blocked, please do one of the following:

  • Directly request the IT Admin of the recipient domain to unblock Zoho CRM.
  • Or write to Zoho CRM Support at with details of the recipient email address. We will do what is required to whitelist Zoho CRM.

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