Setting up multi-cloud email service on AWS

The project was to deploy a Multi Cloud Server in AWS cloud to support the Mail service solution for a leading Automobile dealer. 


The project was initiated with the following objectives.

  1. Migrate existing Mail Server from on-premise to the Cloud infrastructure with 0% data loss and minimum downtime. 
  2. Deploy the Mail Server solution to support large email accounts and maintain high availability.
  3. The administration of the mail server should be simple and should be simple for a layman.
  4. Use AWS infrastructure to host the email services, where priority is given to performance and reliability.
  5. Browser-based client interface.
  6. Setup Zimbra Web Client to manage user access to all the ZCS features.


  1. Email is a business-critical IT function and the client could not afford email system outages or data loss.
  2. Migrating 3000+ mailboxes was quite a challenge since emails would have to be moved to the new cloud infrastructure without disrupting the Client’s workforce.
  3. Maintain faster, uninterrupted, and highly reliable email communication.
  4. A large number of email accounts need to be migrated.
  5. Use open-source edition of software due to financial constraints.


The Zimbra Collaboration Suite was implemented to provide an end-to-end mail solution that is scalable and highly reliable. The messaging architecture is built with well-known open-system technology and standards and is composed of a mail server application and a client interface. For Horizontal scalability, a separate mailbox server with its own data store, message store, and set mailbox accounts was implemented as a solution for this client. To scale for additional mail accounts, we can easily add more servers for mail boxes..

Zimbra multi-server architecture-AWS Cloud environment

The inbound Internet mail goes to any of the Zimbra MTA servers and goes through spam and virus filtering. The designated Zimbra MTA server looks up the addressee’s directory information from the Zimbra LDAP replica server. After obtaining the user’s information from the Zimbra LDAP server, the MTA server sends the mail to the appropriate Zimbra server. Internal end-user connections are made directly to any Zimbra server which then obtains the user’s directory information from Zimbra LDAP and redirects the user as needed.

Tools Used: 

The recommended method for migrating users to Zimbra from an existing IMAP server is with the imapsync tool written by Gilles Lamiral. We used a custom bash script to automate the migration of email accounts using the imapsync tool. 


The migration, testing, and the rollout happened seamlessly; now, Client’s users can easily access their email, contacts, and calendars on-the-go using the Zimbra Mobile Web.


Leave a Reply