Office 365: E-mail Statistics (Over 90 Days)

$EmailAddress = "user@acmecorp.com"
$FromDate = "2025-12-01"
$ToDate = "2026-05-31"
$SearchName = "Mail_Count"
$CaseName = $SearchName + "_Case"

Connect-IPPSSession -EnableSearchOnlySession
$query = '(To:"'+$EmailAddress+'" OR Cc:"'+$EmailAddress+'") AND Received:'+$FromDate+'..'+$ToDate
New-ComplianceCase $CaseName
New-ComplianceSearch -Name $SearchName -ExchangeLocation All -ContentMatchQuery $query
Start-ComplianceSearch $SearchName
do {
    $status = (Get-ComplianceSearch -Identity $SearchName).Status
    
    Write-Host "Current status: $status - $((Get-Date).ToString('HH:mm:ss'))"
    if ($status -notin @("Completed", "Failed", "PartiallyCompleted")) {
        Start-Sleep -Seconds 15
    }
    
} while ($status -notin @("Completed", "Failed", "PartiallyCompleted"))

https://purview.microsoft.com/ediscovery/casespage

At this point, you need to go to Purview, open the case, open the search and do an export.

Put the CSVs in a folder, change the path at the top and run this:

$sourceFolder = "C:\xxx"

Get-ChildItem -Path $sourceFolder -Filter "*.csv" | ForEach-Object {
     Write-Host "Processing file: $($_.Name)..." -ForegroundColor Cyan
     Import-Csv $_.FullName
} | Where-Object { !([string]::IsNullOrWhiteSpace($_.Date)) } | Select-Object @{
     Name = "Month"
     Expression = { 
          # Substring extraction handles ISO-8601 strings quickly
          $_.Date.Substring(0, 7) 
     }
} | Group-Object Month | Select-Object @{Name="Reporting Month"; Expression={$_.Name}}, Count | Sort-Object "Reporting Month" | Format-Table -AutoSize