Email Migration Mistakes to Avoid at All Costs

Migrating mailboxes between systems (e.g., from GoDaddy Microsoft 365 to a tenant managed by you, or from Google Workspace to native Microsoft 365) seems simple on paper. You copy mail, repoint DNS, and log in.

But in practice, email migrations are high-risk operations. A single mistake can lead to permanent data loss, day-long downtime, and broken external communication.

Here are the most common migration failure modes we've resolved.

1. Migrating Without a Cold Backup

Do not rely solely on migration tools (like BitTitan MigrationWiz or AvePoint) to sync data. If a tool fails mid-sync, or if a user deletes a folder during the cutover, you need an independent offline copy.

The Fix: Export mailbox contents to PST files or run a full tenant-level backup prior to modifying any MX or DNS settings.

2. Incomplete DNS TTL Decreases

DNS records are cached by servers across the internet based on their Time-To-Live (TTL) value. If your MX record TTL is set to 24 hours, and you change the record to point to the new provider, some mail servers will continue sending mail to the old provider for up to a full day.

The Fix: Lower your DNS TTL values to 300 seconds (5 minutes) at least 48 hours before the migration cutover. This ensures the routing change propagates globally almost instantly.

3. Ignoring Alias and Shared Mailbox Layouts

During migrations, engineers often focus entirely on primary user accounts and forget aliases, distribution lists, and shared mailboxes (e.g., info@, billing@). If these are not provisioned in the destination tenant prior to MX record change, incoming mail to those addresses will bounce.

The Fix: Map out your entire source directory, extracting all SMTP addresses, shared mailboxes, and distribution lists. Pre-configure them in the destination tenant.

4. Failing to Defederate GoDaddy Properly

If you are migrating off GoDaddy Microsoft 365 to a direct tenant, you must defederate the domain. If you do not follow the PowerShell defederation steps correctly, the domain will remain linked to GoDaddy's identity server, blocking users from logging in or authenticating natively.

Avoid these mistakes by working with a certified migration expert to ensure zero downtime.