First, choose the domain for which you want to configure the routing and provide the other parameters based on your requirement. When you have configured the MX records to deliver emails to Zoho Mail, you can further configure advanced delivery options, to route emails to a different destination server based on the email delivery option chosen.
Split Delivery: Deliver Emails to Non-existing accounts only
You can configure Split Delivery when you have a set of accounts in Zoho Mail and the remaining accounts on the other server. When you choose this option, the emails that arrive to the accounts that exist in Zoho are delivered in Zoho. When an email arrives to an account, that does not exist in Zoho, the email will be redirected to the selected destination server, instead of bouncing back the email.
Dual Delivery: Parallel email delivery for existing accounts only.
You can configure Dual Delivery when you want the email delivery in both servers for all the existing accounts in Zoho. In case an email arrives to a non existing account, the email will be bounced back directly from Zoho servers and will not be checked in the destination servers. Essentially, Dual Delivery can be configured when you have an email backup or archival service elsewhere or want both the systems to co-exist due to various reasons.
Email Routing: Route all emails irrespective of account in Zoho.
You can configure the 'Email Routing' option in Zoho Mail, when you want all the emails addressed to your email to be routed, irrespective of whether the account is setup in Zoho or not. The emails will be delivered to Zoho accounts if it is setup.
Parameters required to configure the Delivery options:
Destination Server: The destination server is a valid domain name or the valid email servers that can receive emails directly. When a domain name is provided in the destination, the routed emails will be delivered to the MX records of the domain which has been provided as the destination. In case MX records are provided directly in the destination, the emails will be directly routed to the provided servers.
Change SMTP envelope: When you provide another domain as the destination server, ex: mydestination.com, you may want the emails to be delivered to firstname.lastname@example.org in the other server. If the SMTP envelope option is enabled, when the emails are routed, the email will be sent to the email address email@example.com, when the emails are actually sent to firstname.lastname@example.org. This depends on your choice and based on your decision to provide the destination as server name or domain name.
Send bounce when mail to the destination fails: When you enable routing to the destination servers, mail to the destination may fail due to various reasons. If you enable the Send bounce option, the bounced email will be sent to the sender. You may enable or disable the bounce emails to the sender using this option.
Verification Email Address: Before email routing can be enabled, a verification email will be delivered to the routed server to confirm the validity of the chosen destination server details. You need to provide a valid email address to which a verification email will be sent. Only if the email has been successfully delivered, the email routing can be enabled.
The Incoming and Outgoing gateways are generally used when you use third party systems for services like Email Archival, Backup or Retention for corporate policies. The third party service will provide you the MX records or IP Address, to use with their services and the IP address from which the copy will be routed to Zoho Mail.
You need to configure the IP address provided by the third party service as 'Incoming Gateway'. Similarly, to route your outgoing emails through the third party service, you need to configure the MX or IP address where the service accepts email for backup, as Outgoing Gateway. You can refer here for details about backup options available in Zoho Mail.
An outbound email gateway is another server which is configured to relay the outgoing servers of various domains of your organization.
You can configure outbound gateway when you want to relay all the outgoing emails from your server to another SMTP server. The other server will deliver the emails to the respective accounts specified for recipients. The other server may archive emails for backup or email retention purposes.
An inbound gateway is the server which routes the emails to the Zoho Mail Servers. If the MX records of your domain is pointed to a legacy server or a backup server, you may configure email routing from your legacy server to Zoho, where the MX is not pointed to Zoho. In such cases, you need to provide the IP addresses of the servers, which relay emails to the accounts here. This will ensure that the configured IP addresses are considered as legitimate and whitelisted for your organization.
For newly signed up users (Free plan), Email routing will not be available. Refer here for more details.