Setting up Email Relay | Online Help - Zoho CRM

Setting up Email Relay

Understanding Email Relay and its benefits

Email Relay allows you to route emails through your (company's) server while sending emails from Zoho CRM. Once the relay server is set up, the sent emails will follow a path like this:  Zoho CRM -to- Relay server -to- Recipient

Sending emails through a relay server lets you combat spamming or mislabelling when large batches of emails are sent. Many businesses that send out bulk emails like newsletters, notifications, invitations, automatic transactional emails etc. to their customers regularly, face higher chances of spamming and sometimes even the authenticity of an email becomes questionable. In such cases, a relay server can be beneficial. Let's see some of the benefits that relay servers can provide:
  1. Not all, but few organizations are required to store copies of emails that are sent to the recipients as part of their compliance goals. If the emails are routed through the relay server, you can always keep a backup of the sent emails in the server.

  2. Often, important transactions and messages are shared with the customers via email. It's best to have access to all such emails and attachments sent by your employees even after they discontinue service in your organization. You may need them for reference in the future.

  3. Sometimes emails are prone to virus threats and to prevent a potential malware attack on the recipients' systems, it's best to run antivirus checks on the outbound emails before sending it to the customers.

  4. The bulk emails are intended to address a large population and therefore consist of content that is common for all the recipients. Just in case, you want to share some additional information such as disclaimers, notices or promotions with selected sets of customers, then instead of sending separate emails, you can just append the information to the outbound emails before sending. 

  5. Oftentimes emails are prone to spoofing, where the email header is tampered with to give an appearance of spam email. Sending emails from the relay server can help you avoid it. 

  6. The bounced and failed delivery emails can be accessed from the relay server.

Points to consider before setting up a relay server

  1. You can only send emails that originate from Zoho CRM via the relay server. That is workflow emails, individual emails, and mass emails. You may choose to send all or either of these emails from a relay server.
  2. You can manually set limits to the number of emails (only the above-mentioned emails) that can be sent from the relay server. 
    Note that sending emails through the relay server does not change the email limit that is set for an edition. For example, as per the subscribed CRM edition if your daily limit for sending emails is 5000 emails/day, then you can set aside some number of emails, like 2000 to be sent from the relay server. The remaining 3000 emails will be sent from the Zoho CRM server. 
  3. Emails that are sent from the Zoho CRM's server will continue to be sent from this server and the per-day limits of the outbound emails will depend on your subscription. 
  4. It is advisable to whitelist all the IP addresses of Zoho CRM in your relay server to avoid any deliverability issues. But, note that whitelisting IPs may be necessary if you set up an open relay server (an SMTP server that allows not just mail destined to or originating from known users but every user to send emails). 

Authenticating Email Protocols In Relay Server

When a relay server is not set 

The outbound emails originate from the user's domain ( and are sent to the recipient via Zoho CRM's server. To receive the delivery failed and bounced emails, the return path (variable envelope from address) is set to Zoho CRM's server. This change causes a mismatch of IP addresses between the originating email and return path that fails an essential email authentication protocol, called SPF. To avoid deliverability issues, Zoho CRM signs DKIM (alternate email authentication protocol). Signing DKIM ensures that the emails pass the DMARC policy and are successfully delivered.

When a relay server is set

The outbound emails are sent from Zoho CRM's server to the relay server from where they are sent to the recipients. Some vendors tend to change the return path of the emails to their server to manage the bounced and failed delivery emails within the relay server. 
Note: If you want to access the bounced emails (stored in the relay server) within CRM, you can do so by fetching the bounce management data from the relay server and integrating it with CRM using API. 
Once a relay server is set there are two possibilities concerning the return paths: 
  1. If the return path is retained as Zoho CRM's server
    1. The outbound email is sent from Zoho CRM's server to the relay server. At this point, the IP address of the originating email is authenticated against the IP address mentioned in the return path. Since the return path is retained to Zoho CRM's server, both the IP addresses will match resulting in SPF validation to pass. 
    2. The email is then sent to the recipient from the relay server, at this point another IP address authentication will be carried out between the email origination and return path. This time, the originating email's IP address is the relay server and the return path's IP address is Zoho CRM's server, which will cause SPF failure due to a mismatch of IP addresses. Because of this, the email deliverability will be unsuccessful and the email may land as spam in the recipient's inbox. 
To prevent such instances, it is recommended to enable DKIM (it automatically passes the DMARC policy) which in turn ensures successful email delivery.
  1. If the return path is set to relay server
    1. The outbound email is sent from Zoho CRM's server to the relay server. An IP address authentication is carried out and the originating email's IP will match with that of the return path which will result in SPF validation. 
    2. The email will be sent to the recipient from the relay server and the IP authentication will display a match of IP addresses because in this case, both the originating email and return paths have the same IP addresses (relay server). This will result in SPF validation and the email will be delivered successfully.  
  • The return path is by default set to Zoho CRM's address and many vendors don't change it to relay server's address. Since SPF failure in these cases is inevitable, it is mandatory to enable DKIM and ensure the DMARC policy is signed. 

  • We recommend you sign DKIM with Zoho CRM to rule out any possibilities of unsuccessful delivery. However, you can enable it with the vendor too.

Whitelist Zoho CRM IPs in the Relay Server

Emails may be sent to the relay server from different IP addresses of Zoho CRM and to prevent any unsuccessful deliveries as a result of IP mismatch it is essential to whitelist all our IPs in the relay server. It is mandatory to whitelist the IPs if an open relay server (it uses IPs as a criteria to filter the inbound emails) is used. Though it is not necessary, to whitelist these IPs in the relay servers that use the host's username and password as an authentication mechanism, it is still recommended to publish these IPs in the relay servers.

Server Name (Accessing URL)
IP addresses















































    CN DC








      JP DC













      Setting up a Relay Server

      You can route the emails sent from Zoho CRM's server to your company's server using email relay. Based on your CRM subscription, you can add multiple domains and set relay servers for each domain. You can add a maximum of three relay servers in a single domain. Before you begin setting up the email relay, make sure you have the following information from your email administrator: 
      • Port number - The port number of your company's SMTP server. The Email relay supports the following port numbers: 25, 465, 587. 

      • Secure connection - Whether you choose an SSL or TLS certificate, it is advisable to authenticate the certificate (authenticating the certificates is not a mandatory step). To do so, you will need to mention the host's name and password on the certificate.  

      Permission Required  
      Users with administrative permission in their profile can access this feature.  

      Setting the type of emails sent from the relay server 

      You can select the type of emails that should be sent via the relay server. Only the emails that originate from CRM such as workflow emails, mass emails or individual emails can be sent through a relay server. You can use different relay servers for each type of email, for example, you can use server one to send all the mass emails and server two to send all the workflow-related emails.  

      Setting daily email limit from the relay server  

      You can specify the number of emails that should be sent daily from the relay server. Once the maximum limit is reached, the subsequent emails will be sent from the CRM server. 

      Managing bounced emails

      Bounce management with Zoho CRM provides an option to configure an email address to which the bounced emails will be sent. Say, when you send out packages using any delivery services company, you mention the recipient’s address and the address the package must be returned to in case the package couldn’t be delivered. Similarly, the emails we send out have the recipient’s address and a return path. A return path is an email address where the emails that couldn’t be delivered are returned. In CRM, the default return path is the Zoho CRM mailbox and it processes the bounced emails by updating the email status to 'Bounced' in Zoho CRM under the related lists, sales signal, reports and smart filters. 
      1. With the 'Bounce management with Zoho CRM' option, Zoho CRM will be set as the return path to receive bounce emails. i.e. Whenever an email gets bounced, the bounce report will be sent to the Zoho CRM mailbox and the email status will be updated as 'Bounced.
      1. Some relay servers accept addresses as return paths that are already configured with the relay server. In that case, users can configure the server to allow the following domains. Update these DC-specific domains in your relay server to continue receiving bounce mail reports back to Zoho CRM.







      1. When the relay server does not allow Zoho CRM as the return path then the user should disable Bounce management in the Zoho CRM option and set the return path as the relay server in two ways:
        1. Set 'From address' as the default return path – The sender 'From email address' will be set as the return path and the bounce report (if the mail is bounced) will be directly sent to this address.
        2. Set custom email address as default return path – The user can set an email address, belonging to the domain configured with the relay server, as the return path. This option is ideal when the user wants to receive the reports of bounced emails, originating from different 'From addresses' in a common mailbox. Say for instance you have the following email addresses -,, and You can set a common email address as the return path which receives the reports of bounced emails, originating from the email addresses mentioned above.

      By disabling 'Bounce management with Zoho CRM', the user will not get a bounce mail notification inside CRM and the email status will not be updated as 'Bounced' in the email-related list.

      To configure the email relay setting 
      1. Go to Setup > Channels > Email > Email Deliverability > Email Relay

      2. In the Email Relay Settings page, click  + New Server. 

      3. In the Add New Server page, enter the details. 

      4. In the Server Details section, do the following:

        1. Enter the Server Name

        2. Choose a Port number from the drop-down list. 

        3. Specify the Daily mail limit.

        4. Choose either of the Secure connections: SSL, TLS, or Never. 

      5. In the Domain Settings section, do the following:

        1. Domain in this server: Select a Domain from the drop-down list. 

        2. All the domains that you have added for Email authentication will be listed here. You can also add a new Domain.  

        3. Type of email: Select the types of email from the drop-down list. 

        4. DKIM Authentication: Check Enable, to allow Zoho to sign DKIM for the emails routed via the relay server.  

          Click Copy to Clipboard and paste the public key in your DNS setting. Choose a  Port number from the drop-down list. 

        5. Check Bounce Management with Zoho CRM if you want the bounced emails to be returned to Zoho CRM.

          Uncheck if you want to set the desired Return Path: Enter the desired email address if you choose a custom email address as the default return path.

      6. In the Authentication section, do the following:

        1. Click Yes or No for whether authentication is required or not.

        2. If you choose Yes, enter the host's Service provider, Username and Password for authentication.

        3. For supported email service providers, you will be prompted to log in via OAuth.

        4. In case your service provider is not listed, choose others from the dropdown, and log in via the traditional password-based login method.

      7. Click Configure.

      Note: If the maximum limit to send emails in a relay server is reached, the subsequent emails will be sent from the CRM server.

      View Server information

      Under server information in the Email Relay Settings page, you will be able to view all the configured servers. In case you are not using a server temporarily, you can toggle it off. You can also delete a server if you want to discontinue sending emails from it.  

      1. You can set a maximum of five domains depending on your CRM subscription. You can configure multiple relay servers (up to five) for a single domain. 
      2. Due to any reason, if the outbound emails fail to deliver from the relay server they will be sent via the Zoho CRM's server. 
      3. After three repeated failures (in a day), the user will be sent a warning email notifying the same. The relay server will not be used to send emails until the next day.  

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