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These scripts cover day-to-day Exchange Online administration tasks: reporting on mailbox sizes, managing distribution groups, and configuring mail flow rules. All scripts target Exchange Online via the ExchangeOnlineManagement module, though many cmdlets are compatible with on-premises Exchange Server as well.

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Prerequisites

# Install the Exchange Online Management module
Install-Module -Name ExchangeOnlineManagement -Force

# Import the module
Import-Module ExchangeOnlineManagement

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Connecting to Exchange Online

1

Install the module

Install-Module -Name ExchangeOnlineManagement -Force
2

Connect with your admin account

Connect-ExchangeOnline -UserPrincipalName admin@yourdomain.com
You will be prompted for MFA if your account requires it. After authenticating, your session is active for all subsequent Exchange cmdlets.
3

Verify the connection

# Confirm you can retrieve mailbox data
Get-Mailbox -ResultSize 5 | Select-Object DisplayName, PrimarySmtpAddress
4

Disconnect when finished

Disconnect-ExchangeOnline -Confirm:$false
Use a dedicated service account or Global Admin with appropriate Exchange roles. The minimum role for most read operations is View-Only Recipients.

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Mailbox management

Common cmdlets for working with user and shared mailboxes. 
# List all mailboxes
Get-Mailbox -ResultSize Unlimited

# Get a specific mailbox
Get-Mailbox -Identity user@yourdomain.com

# Get mailbox statistics (size, item count)
Get-MailboxStatistics -Identity user@yourdomain.com | 
    Select-Object DisplayName, TotalItemSize, ItemCount

# Get statistics for all mailboxes
Get-Mailbox -ResultSize Unlimited | 
    Get-MailboxStatistics | 
    Select-Object DisplayName, TotalItemSize, ItemCount |
    Sort-Object TotalItemSize -Descending

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Mailbox size report

Generate a CSV report of all mailbox sizes across your tenant. 
# Run the mailbox size report script
.\Exchange\Get-MailboxSizeReport.ps1 -ExportPath "C:\Reports"
The -ExportPath parameter specifies the directory where the CSV report is saved. The script enumerates all mailboxes, retrieves statistics for each, and exports the results. 
# Manual equivalent — build the report inline
$report = Get-Mailbox -ResultSize Unlimited | ForEach-Object {
    $stats = Get-MailboxStatistics -Identity $_.PrimarySmtpAddress
    [PSCustomObject]@{
        DisplayName       = $_.DisplayName
        EmailAddress      = $_.PrimarySmtpAddress
        MailboxType       = $_.RecipientTypeDetails
        TotalItemSize     = $stats.TotalItemSize
        ItemCount         = $stats.ItemCount
        LastLogonTime     = $stats.LastLogonTime
    }
}

$report | Export-Csv -Path "C:\Reports\MailboxSizes.csv" -NoTypeInformation
Write-Host "Report saved to C:\Reports\MailboxSizes.csv"

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Distribution groups

# List all distribution groups
Get-DistributionGroup -ResultSize Unlimited | 
    Select-Object DisplayName, PrimarySmtpAddress, GroupType

# Get members of a specific group
Get-DistributionGroupMember -Identity "it-team@yourdomain.com" | 
    Select-Object DisplayName, PrimarySmtpAddress

# Add a member to a distribution group
Add-DistributionGroupMember -Identity "it-team@yourdomain.com" `
    -Member "newuser@yourdomain.com"

# Remove a member from a distribution group
Remove-DistributionGroupMember -Identity "it-team@yourdomain.com" `
    -Member "leavinguser@yourdomain.com"

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Mail flow rules

# List all transport rules (mail flow rules)
Get-TransportRule | Select-Object Name, State, Priority

# Get details of a specific rule
Get-TransportRule -Identity "Block External Forwarding" | 
    Format-List

# Disable a transport rule
Disable-TransportRule -Identity "Rule Name"

# Enable a transport rule
Enable-TransportRule -Identity "Rule Name"
Changes to mail flow rules take effect immediately in Exchange Online. Test new rules using the audit mode (SetAuditSeverity action) before enabling enforcement.

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