User's mailbox Limit not retained after cross forest migration

1. Mailbox Limit Preservation Methods:

1. PowerShell Approach

# Export existing mailbox settings before migration
Get-Mailbox -Identity "UserName" | Select-Object ProhibitSendQuota, ProhibitSendReceiveQuota, IssueWarningQuota

# After migration, apply these settings to the new mailbox
Set-Mailbox -Identity "NewUserName" `
    -ProhibitSendQuota <PreviousValue> `
    -ProhibitSendReceiveQuota <PreviousValue> `
    -IssueWarningQuota <PreviousValue>

Migration Best Practices:

• Use Microsoft Exchange Migration Tools
• Leverage MigrationEndpoint configuration
• Utilize Hybrid Configuration Wizard for seamless migration

1. Specific Considerations:

• Mailbox size limits are stored in Active Directory
• These settings are not automatically carried over during cross-forest migration
• Manual configuration or scripting is required

1. Recommended Migration Process: a) Document existing mailbox limits before migration b) Create a migration spreadsheet tracking:
   • Current mailbox limits
   • User properties
   • Specific configuration details
2. Advanced Migration Script Example:

# Function to migrate mailbox limits
function Migrate-MailboxLimits {
    param(
        [string]$SourceUser,
        [string]$DestinationUser
    )

    $SourceMailbox = Get-Mailbox -Identity $SourceUser -ReadOnly
    $LimitSettings = $SourceMailbox | Select-Object ProhibitSendQuota, ProhibitSendReceiveQuota, IssueWarningQuota

    Set-Mailbox -Identity $DestinationUser `
        -ProhibitSendQuota $LimitSettings.ProhibitSendQuota `
        -ProhibitSendReceiveQuota $LimitSettings.ProhibitSendReceiveQuota `
        -IssueWarningQuota $LimitSettings.IssueWarningQuota
}

1. Alternative Solutions:

• Third-party migration tools (Quest, BitTitan)
• Microsoft 365 migration tools
• Exchange Online migration wizard

1. Potential Challenges:

• Different forest configurations
• Varying Exchange versions
• Security and permission constraints