Email Delivery and Bounce - Zoho Desk Knowledgebase

Understanding Email Delivery and Bounce

When you need to get an important message to a customer, one of the fastest ways to do it is by email. Despite several new and modern communication techniques, email stays the most preferred channel for customers when they need help from a business.

However, what is often overlooked, is to ensure seamless delivery of emails to your customers. We've all been there. You draft an email ticket, send away, and then — when you check your ticket — you see that it “bounced.” Or worse you send out instant notifications that never reach your customers.

In this article, let's talk about the following:
  • What are bounces and why do they happen?
  • What is the impact of bounce?
  • What is your way out of a bounce bounty?

What are Bounces?
Bounces are those email addresses to which Zoho Desk could not deliver your email. They usually appear as a new conversation in your ticket. But there's no way to identify bounces in notification emails unless you take a closer look—at ticket history. There are two kinds of bounce email:
  • Hard bounce
  • Soft bounce

Hard Bounce
A hard bounce is that email address to which an email is permanently undeliverable by Zoho Desk for different reasons. Some of them are as follows:
  • The recipient email address does not exist.
  • The domain name does not exist.
  • The mail server of the recipient has blocked delivery.

Soft Bounce
A soft bounce is a temporary failure, and there is a chance that the recipient will receive the email from Zoho Desk eventually. It can happen when:
  • Your email response is too large.
  • Customer's inbox is full.
  • The recipient's server is down or offline.

What is the impact of bounce?
Zoho Desk takes bounces seriously as they affect not only the delivery of your emails but also the reputation of the email service used to send the emails, in this case, Zoho. We monitor for accounts that continually send emails to invalid contacts and block the email addresses from time to time. If you can't send emails to a contact, it means that one of the following factors impact your account: 
  • When an email has hard bounced, it will be blocked by Zoho Desk permanently. 
  • 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 Desk 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.

What is your way out of a bounce bounty?
It can be frustrating when you send out a ticket reply or notification email, and it does not get delivered. Maybe that one of the bounce mitigation factors has kicked in for your account. But, not all bounces are permanent.

An email address that has been marked as a "hard bounce" can be removed from the blocked list. If you're convinced that the contact's email address is valid, write to Zoho Desk Support at

If your account reaches too high of a bounce rate, your email sending can be blocked without warning. This block applies only to your email notifications and not for ticket responses. If you find yourself in this situation, write to Zoho Desk Support at We will do what is required to whitelist Zoho Desk.

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