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Knowledge Center

Mail Migration

You can migrate emails from external sources (e.g., Gmail or on-premises email servers) to Synology MailPlus Server for centralized management.

Task Setup

Go to Server Management > Mail Migration and click Create to launch the migration window. See the following sections for detailed instructions.

To define general task settings:

Go to General to specify basic information:

  • Task: Enter a task name.
  • Select the server type: Select from external email providers like Gmail, or email servers like Microsoft Exchange.
    • Google Workspace: Migrate via Gmail API. Create a service key and upload it by clicking on the folder icon.
    • Microsoft 365: Migrate via Microsoft 365 API. Sign in to your Microsoft account. The sign-in process will use OAuth 2.0 for secure authentication.
    • Other server types: Migrate via IMAP.
  • Server address: Specify the source server IP address or domain name.
  • Port: Specify the source server port.
  • Enable secure connection (SSL): Select to migrate emails over SSL connection.
  • IMAP path prefix: Depending on the source server type, specify the IMAP path prefix (a prefix applied to all folders, usually used as the IMAP namespace for the folder names):
    • On-premises IMAP servers and Microsoft Exchange: Check the server settings to find out the information.
    • Third-party email services: Gmail and Yahoo Mail have a blank IMAP path prefix; for other services, enter INBOX (commonly used) or consult the relevant documentation for details.
  • Migrate mail with the delegate account (for Microsoft Exchange): Select to specify a delegate account that has full access permissions to all source accounts. With the delegate account, you can migrate emails without asking for each account's credentials.
  • Accounts to migrate per time period: Define how many source accounts will be migrated per work session.
  • Schedule email migration: Set a schedule for the task to avoid heavy traffic time.

Note:

  • The task name cannot be specified as ".." or ".".
  • The task name cannot contain any of the following characters: / \ : "
  • You must select Enable SMTP at Service > Protocol > SMTP to receive success or failure notifications.
  • If you provide an IP address as the Server address, success or failure notification may not be sent.
  • When the source server is Gmail/Google Workspace or Yahoo!, check the additional requirements below:

To set up email and mailbox filters:

Go to Filter and specify which messages and mailboxes to migrate.

  • Discard mail received before the date and Discard mail received after the date: Discard emails received before or after the specified date during migration. Emails received on the specified date will be kept.
  • Skip trash mail and Skip spam mail: Skip mailboxes that carry the "\Trash" or "\Junk" attribute as defined in RFC6154.
  • Maximum size per email (KB): Specify the maximum size of an email to migrate.
  • Enable mailbox filter: Decide which mailbox to skip or migrate by keyword:
    • Skip mailboxes by keyword and Migrate mailboxes by keyword: Select a filter policy.
    • Set Keywords: Click to add keywords:
      • Keyword: Mailboxes matching the keywords here will be processed according to the filter policy.
      • Exceptions: Mailboxes matching the keywords here will not be processed according to the filter policy.

Note:

  • When you migrate emails from Google Workspace, filters will be applied according to labels.
  • You can set a regular expression as a filter. Please add a slash (/) before and after the regular expression (e.g., /^RegExp$/).

To receive migration notifications:

Go to Notification to set up notification preferences.

  • Send success notification: You will receive notifications when each account's email migration is complete. You can further decide where the notification should be sent.
  • Send failure notification: You will receive notifications when an account's email migration fails. You can further decide where the notification should be sent.

To import the user list:

Go to User List to import user data.

  1. Prepare a user list following the requirements below:
    • The user list should be a CSV file. It can be generated with a text editor.
    • List one user account in one row.
    • List each user's following information from left to right: source account, source account's password, and destination MailPlus account.
  2. In a CSV file, each piece of information is separated by a comma.
    Example of a list:
    User1's source account,User1's source account password,User1's MailPlus account
    User2's source account,User2's source account password,User2's MailPlus account
    User3's source account,User3's source account password,User3's MailPlus account
  3. Go to User List to import:
    • Import: Click to import a user list.
    • Delete: Click to delete an unwanted user's data.
    • Check: Click to check if all the imported source accounts are correct and if all the corresponding MailPlus accounts are activated.

Note:

  • Passwords of the source accounts can be omitted (i.e., Source account,,MailPlus account) under the following circumstances:
    • The source server is set to Microsoft Exchange and Migrate mail with the delegate account is enabled.
    • The source server is set to Google Workspace.
  • Google Workspace accounts should be specified using FQDA (i.e., username@domain name).
  • Source accounts and MailPlus accounts cannot contain the ":" character.
  • For detailed instructions, refer to the following documents:

Task Management

Once a migration task is fully set up, you can manage it and view its status.

To view task status:

  1. Go to Server Management > Mail Migration.
  2. Click Information (the document icon) to check the task summary and logs.

To run a task:

  1. Go to Server Management > Mail Migration.
  2. Select a task and click Start.

Note:

  • To avoid migration errors, do not do either of the following during the migration:
    • Changing the IMAP/POP3 settings on MailPlus Server
    • Moving or deleting emails on the source server
Task Setup
Task Management