Email Migration Without Interruption: Our Proven Method

The number one fear during an email migration? Losing messages or experiencing a service outage. Good news: with the right method, your migration can be completely seamless. Here\'s how we do it at InfoSwitch.

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The Principle: Background Migration

The key idea is to never shut down the old system before the new one is 100% operational and synced. Throughout the entire migration, you continue working normally.

Phase 1: Preparation (D-7 to D-3)

Creating the Target Environment

• Setting up the Infomaniak Mail Service
• Configuring mailboxes (same addresses)
• Setting up aliases and redirections
• Preparing DNS records (without applying them)

Reducing the DNS TTL

The TTL (Time To Live) indicates how long DNS servers cache your records. By reducing it in advance:

• Lower the TTL from 3600 (1 hour) to 300 (5 minutes)
• Wait 24-48 hours for the change to propagate
• The final switch will be much faster as a result

Phase 2: Synchronization (D-3 to D-1)

Background IMAP Migration

We use IMAP migration tools that:

• Connect to the old server in read-only mode
• Copy all emails to the new server
• Preserve the folder structure
• Retain dates and statuses (read/unread)

Meanwhile, you continue using your old email normally.

Incremental Synchronization

Once the initial copy is complete, we enable incremental synchronization:

• New emails arriving on the old server are automatically copied
• Changes (deletions, moves) are reflected
• Both servers stay in sync until the switch

Phase 3: DNS Switch (D-Day)

Choosing the Right Moment

We schedule the switch during a low-activity period:

• Early morning (6-7am)
• Weekend
• Outside critical periods (month-end, events...)

Changing MX Records

We update the MX record to point to Infomaniak:

DNS Propagation

Thanks to the reduced TTL, propagation is fast:

• 5-15 minutes for most servers
• Maximum 1-2 hours for the slowest ones

Phase 4: Dual Reception (D to D+2)

Why Dual Reception?

During DNS propagation, some servers still send to the old host. To avoid losing anything:

• The old server remains active for receiving
• We set up automatic forwarding to the new one
• Any email arriving at the old server is immediately forwarded

Recommended Duration

Maintain dual reception for 48 to 72 hours to ensure all emails in transit are captured.

Phase 5: Workstation Configuration (D to D+3)

Progressive Approach

We configure user workstations after the DNS switch:

1. The user connects to the new server
2. They find all their emails (already synchronized)
3. New emails arrive directly on the new server

No Productivity Loss

During workstation configuration:

• The Infomaniak webmail is immediately accessible
• Users can work without waiting
• Desktop clients are configured progressively

Handling Special Cases

Emails Sent During Migration

Emails you send during the migration go out normally from your email client. They are sent via whichever server is configured in your client (old or new depending on the stage).

Replies to Old Emails

Replies are sent to the email address, not the server. They therefore follow the active MX record and arrive at the right place.

Mailing Lists and Newsletters

Marketing emails arrive normally. The MX switch is transparent to senders.

What Can Go Wrong (and How to Avoid It)

Typical Migration Timeline

Conclusion

A zero-downtime email migration is entirely possible with the right method. The key is to never shut down the old system before the new one is fully operational.

At InfoSwitch, this is the method we apply every time. Result: zero lost emails, zero service interruptions.

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