Cloudiway has two tools to help you. Using Cloudiway’s tools you can either:
- Apply forwarding rules on user mailboxes. Or:
- Route emails to the correct address before they even get to your tenant.
The overall concept of how to coexist during a migration is challenging at best.
There is no magic button that makes a migration project perfect from every perspective. You just have to choose a path and go for it!
During a staged migration where you migrate batches of users at a time, you will want your users to be able to send emails to each other across the tenants, but the users will not know to which mailbox they need to send an email.
For example, users that are still in the source tenant will not log in to their target tenant mailboxes to read their email, and vice versa. If a user is cutover to Tenant B, how will they send emails to the users in Tenant A?
Even more critically, when you have the same domain in the source and target tenants, such as with a Google and Office 365 migration, each of those tenants by default will think they are authoritative for your SMTP domain name and will not send emails to that domain outside of their respective tenants.
There are many options to route, forward, re-write, etc., your emails. Exchange, Office 365, and Google Workspace have the ability to create customized rules and routes, but this can be yet another complicated step in an already complex project plan.
In short, the forwarding option is a way for you to apply forwarding rules on individual mailboxes programmatically from the Cloudiway Mail Migration user list.
Just as easily as you can start mailbox migrations, you can click a few buttons to set forwarding rules. You can do this one user at a time or use your batch setup to manage when forwarding is applied.
The forwarding option simply sets a rule on each mailbox to forward emails to another email address. Crucially it does not leave a copy of the forwarded email in the originating mailbox as this would likely lead to duplicate emails during the migration. Based on the mail migration user list, the tools will set forwarding on the target mailboxes back to an alias address on the source user’s mailbox while you migrate the mailbox in the background. When you cut that user or batch over, you can flip the forwarding to send email from the source to the target mailbox so nothing gets missed.
Cloudiway’s Mail Routing tool is part of our Enterprise Coexistence toolset. This includes an option to send outbound emails from all or a subset of users through an outbound mail server that re-writes the SMTP domain to a different domain. This is commonly used in Office 365 tenant-to-tenant migrations where you can’t have the same domain active in two tenants.
An inbound mail server is used to route inbound mail to an alias address before it reaches either tenant. As users are cut over, you update the inbound mapping tool to ensure that external mail flows to the correct mailbox. The inbound server uses a mapping table that you will manually populate and manage throughout the project.
Forwarding vs. Mail Routing: Pros and Cons
Mail Forwarding Pro’s
- Your current tenant routes and rules stay intact. Mail only forwards once it hits the user mailbox.
- Easily managed directly from the Cloudiway User List (which you have already set up for your migration).
- MX Records do not need to be switched (yet).
- Any spam firewalls, such as third party or edge devices, are still used without interruption.
- Don’t worry about hiding addresses in your GAL (Global Address List) because unattended mailboxes will have the forwarding applied to make sure email is delivered to the destination you choose.
Mail Forwarding Con’s
- Outbound SMTP domain rewrites are not performed. (Ask us about using our Outbound re-write tool with the forwarding option!)
- Mailboxes and licenses stay active in both tenants for all users until the project is complete and source mailboxes are decommissioned.
- Users could notice the forwarding rule and remove it without your knowledge.
- Not a great choice for long-term coexistence.
Mail Routing Pro’s
- Mail flow is under your complete control based on one management interface.
- A great choice for long-term coexistence.
- Allows you to limit license usage. You only license and provision target mailboxes at the last minute, and you deprovision source mailboxes right after cutover.
Mail Routing Con’s
- Environments with complex rules and routes, additional spam firewalls, etc., can be difficult to integrate into the inbound and outbound mail flow.
- Requires MX switch.
- Extra hop, and additional mail flow hosting provider (additional point of failure).
- Risk of increased spam scores.
- Unattended mailboxes will receive email and the user may never know.
- Requires very careful planning and updating of the inbound mapping table.