Using Mimecast to Migrate Non US Office 365 to a US Tenant

Migrate Non-US Office 365 to US tenant

Mimecast is a cloud-based, anti-spam and archive-filtering service for securing email accounts and communications for businesses. Mimecast provides end users with cloud-managed services, enhanced security, connectivity and collaboration. Here’s how SkyTerra used Mimecast to migrate a non US Office 365 to a US tenant.


Our client, PharmaEssentia, wanted to give more control over their IT services to their United States-based location due to increasing regulations occurring in Taiwan. They had the unique problem of continuing to appear to the outside world as one entity. Additionally, they needed to designate address book population and communicate their availability to their clients, whether they were free or busy.

Mimecast migration


SkyTerra used Mimecast to migrate a non US Office 365 to a US tenant. First, an inbound email sent to any PharmaEssentia email address is received by Mimecast. The delivery routing policies and the address alteration policy determine if the message is routed to the tenant in Taiwan or the United States. 

With the new system, if the recipient is in Taiwan, the email address remains “” However, if the recipient is a U.S.-based employee, the email address changes to the current location and reflects this change as “” 

Second, outbound emails coming from Taiwan route normally to Mimecast and out to the internet, so an email address like “” leaves Mimecast as the same email address. 

Third, outbound emails coming from the United States tenant routes to Mimecast as “” wherein the address alteration policy applies, changing the email address to 

Lastly, Cloudiway, a Mimecast service, performed a global address sync, and created contacts on both sides for their respective digital mailboxes. Email between the Taiwan and United States tenants now routes internally. 


As a result of the unique solution we crafted, PharmaEssentia’s email communications now reflect one global entity. The company has greater flexibility and control over their internal IT processes. Implementing two new policies – for delivery routing and address alteration – allows for streamlined communication between the United States and Taiwan. 

As an added benefit, Mimecast provides numerous other improvements to PharmaEssentia, including email security and resilience, social engineering defense against phishing attempts, insider risk protection, message encryption and email incident response, among others.

Could Mimecast Work for You? 

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Darren Rathbone

Daren is responsible for working with businesses through their digital transformation journey. He works on Teams/Skype VOIP, Microsoft 365 and Microsoft Virtual Desktop, as well helping clients get more of Azure as they expand in the cloud.