IMAP Migration from Google Workspace to Microsoft 365

Akanksha Chauhan 0 Reputation points
2026-09-14T07:16:18.2433333+00:00

Hello Team,

Greetings!!

We have recently been experiencing significant delays during IMAP migrations from Google Workspace to Microsoft 365 and would like to understand if there are any known issues or recent changes affecting IMAP migration performance.

We are aware that Microsoft provides the native Google Workspace migration method, which would generally be preferable. However, in our migration scenarios, we have split routing/coexistence configured, with the domain configured as Internal Relay in Exchange Online. Because of this setup, we are currently unable to select/configure the required target delivery domain as expected during the native Google Workspace migration process.

Could you please confirm:

  1. Whether there are any known issues, throttling, or performance degradation with IMAP migrations from Google Workspace to Microsoft 365 recently?
  2. Whether the Internal Relay/split-routing configuration can affect the native Google Workspace migration process or the availability of the target delivery domain option?
  3. Is there any recommended configuration or workaround that would allow us to use the native Google Workspace migration while maintaining split routing?

Any guidance or recommended approach would be highly appreciated.

Exchange Online
Exchange Online

A cloud-based service included in Microsoft 365, delivering scalable messaging and collaboration features with simplified management and automatic updates.

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  1. Heimerdinger 380 Reputation points Independent Advisor
    2026-09-14T10:53:15.7233333+00:00

    Hi @Akanksha Chauhan,

    Thank you for posting on the Microsoft Q&A forum.

    Based on my research, the most common factors that can contribute to slower IMAP migrations include migration-service throttling, source-side connection limitations, mailbox size and item count, Google Workspace extraction limits, and overall Microsoft 365 service load. At this time, I am not aware of any recently published service advisory or documented issue indicating a widespread degradation affecting IMAP migrations specifically from Google Workspace to Microsoft 365.

    1. Known throttling or performance degradation IMAP migrations are subject to Microsoft 365 migration-service throttling. By default, Microsoft 365 allows up to 20 concurrent mailbox migrations across migration batches, and this can be increased up to 100 concurrent migrations if the source environment can support the additional load. In addition, Microsoft 365 may apply resource-health throttling when service capacity is constrained. For more information, please refer to: Microsoft 365 and Office 365 migration performance and best practices | Microsoft Learn
    2. Impact of Internal Relay and split-routing configuration Regarding the Internal Relay and split-routing configuration, I was unable to find official documentation that explicitly confirms whether this configuration affects the native Google Workspace migration process or the availability of the Target Delivery Domain option. Since this involves your organization's Exchange Online mail-routing design and coexistence configuration, the behavior may depend on how the routing domains, accepted domains, and migration prerequisites are configured within your tenant. A backend review would likely be required to determine whether the current configuration is preventing the migration service from presenting or validating the target delivery domain as expected.
    3. Recommended configuration or workaround I was not able to find any Microsoft documentation that describes a supported workaround or recommended configuration specifically for using the native Google Workspace migration while maintaining a split-routing/Internal Relay coexistence scenario. Because migration and routing configurations can vary significantly between organizations, I recommend opening a support case with Microsoft. A support engineer will be able to review the backend configuration of your tenant, verify whether the coexistence design is impacting the migration workflow, and provide guidance on the most appropriate migration approach for your environment.

    The Global Administrator should create a service request with Microsoft Support to obtain advanced technical assistance and backend diagnostics. For detailed instructions on how to contact Microsoft Support, please refer to:

    Get support - Microsoft 365 admin.     

    Thank you again for your time and understanding. I really appreciate your patience, and I’m here to help. Looking forward to your response.

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