<#
=============================================================================================
Name:           Audit Email Deletion in Office 365
Description:    This script exports deleted emails audit records to CSV
Website:        o365reports.com


Script Highlights: 
~~~~~~~~~~~~~~~~~
1. The script uses modern authentication to retrieve audit logs. 
2. The script can be executed with MFA enabled account too.   
3. Exports report results to CSV file.   
4. Allows you to track all the deleted emails. 
5. Helps to find out who deleted email from a shared mailbox. 
6. Allows you to generate an email deletion audit report for a custom period.   
7. Automatically installs the EXO V2 module (if not installed already) upon your confirmation.  
8. The script is scheduler-friendly. I.e., Credential can be passed as a parameter instead of saving inside the script. 

For detailed Script execution: https://o365reports.com/2021/09/02/audit-email-deletion-in-office-365-mailbox-powershell
============================================================================================
#>
Param
(
    [Parameter(Mandatory = $false)]
    [Nullable[DateTime]]$StartDate,
    [Nullable[DateTime]]$EndDate,
    [string]$Mailbox,
    [string]$Subject,
    [string]$UserName,
    [string]$Password
)

Function Connect_Exo
{
 #Check for EXO v2 module inatallation
 $Module = Get-Module ExchangeOnlineManagement -ListAvailable
 if($Module.count -eq 0) 
 { 
  Write-Host Exchange Online PowerShell V2 module is not available  -ForegroundColor yellow  
  $Confirm= Read-Host Are you sure you want to install module? [Y] Yes [N] No 
  if($Confirm -match "[yY]") 
  { 
   Write-host "Installing Exchange Online PowerShell module"
   Install-Module ExchangeOnlineManagement -Repository PSGallery -AllowClobber -Force
  } 
  else 
  { 
   Write-Host EXO V2 module is required to connect Exchange Online.Please install module using Install-Module ExchangeOnlineManagement cmdlet. 
   Exit
  }
 } 
 Write-Host Connecting to Exchange Online...
 #Storing credential in script for scheduling purpose/ Passing credential as parameter - Authentication using non-MFA account
 if(($UserName -ne "") -and ($Password -ne ""))
 {
  $SecuredPassword = ConvertTo-SecureString -AsPlainText $Password -Force
  $Credential  = New-Object System.Management.Automation.PSCredential $UserName,$SecuredPassword
  Connect-ExchangeOnline -Credential $Credential
 }
 else
 {
  Connect-ExchangeOnline
 }
}

$MaxStartDate=((Get-Date).AddDays(-89)).Date

#Getting anonymous activity for past 90 days
if(($StartDate -eq $null) -and ($EndDate -eq $null))
{
 $EndDate=(Get-Date).Date
 $StartDate=$MaxStartDate
}
#Getting start date to generate anonymous activity report
While($true)
{
 if ($StartDate -eq $null)
 {
  $StartDate=Read-Host Enter start time for report generation '(Eg:04/28/2021)'
 }
 Try
 {
  $Date=[DateTime]$StartDate
  if($Date -ge $MaxStartDate)
  { 
   break
  }
  else
  {
   Write-Host `nAudit can be retrieved only for past 90 days. Please select a date after $MaxStartDate -ForegroundColor Red
   return
  }
 }
 Catch
 {
  Write-Host `nNot a valid date -ForegroundColor Red
 }
}


#Getting end date to generate external sharing report
While($true)
{
 if ($EndDate -eq $null)
 {
  $EndDate=Read-Host Enter End time for report generation '(Eg: 04/28/2021)'
 }
 Try
 {
  $Date=[DateTime]$EndDate
  if($EndDate -lt ($StartDate))
  {
   Write-Host End time should be later than start time -ForegroundColor Red
   return
  }
  break
 }
 Catch
 {
  Write-Host `nNot a valid date -ForegroundColor Red
 }
}

$OutputCSV=".\DeletedEmailsAuditReport_$((Get-Date -format yyyy-MMM-dd-ddd` hh-mm` tt).ToString()).csv" 
$IntervalTimeInMinutes=1440    #$IntervalTimeInMinutes=Read-Host Enter interval time period '(in minutes)'
$CurrentStart=$StartDate
$CurrentEnd=$CurrentStart.AddMinutes($IntervalTimeInMinutes)

#Check whether CurrentEnd exceeds EndDate
if($CurrentEnd -gt $EndDate)
{
 $CurrentEnd=$EndDate
}

if($CurrentStart -eq $CurrentEnd)
{
 Write-Host Start and end time are same.Please enter different time range -ForegroundColor Red
 Exit
}

Connect_EXO
$CurrentResultCount=0
$AggregateResultCount=0
Write-Host `nRetrieving deleted emails from $StartDate to $EndDate...
$ProcessedAuditCount=0
$OutputEvents=0
$ExportResult=""   
$ExportResults=@()  
$RetriveOperation="SoftDelete,HardDelete,MoveToDeletedItems"

 #Checking whether the user is available
if(($Mailbox.Length -ne 0) -and ((Get-Mailbox -Identity $Mailbox) -eq $null))
{
 Write-Host Mailbox does not exist. Please check the mailbox name. -ForegroundColor Red
 exit
}

while($true)
{ 
 $ResultCount=0
 #Getting email deleted audit data for given time range
 Search-UnifiedAuditLog -StartDate $CurrentStart -EndDate $CurrentEnd -Operations $RetriveOperation -SessionId s -SessionCommand ReturnLargeSet -ResultSize 5000 | ForEach-Object {
  
  $ResultCount++
  $ProcessedAuditCount++
  Write-Progress -Activity "`n     Retrieving email deletion activities from $CurrentStart to $CurrentEnd.."`n" Processed audit record count: $ProcessedAuditCount"
  $MoreInfo=$_.auditdata
  $Operation=$_.Operations
  $AuditData=$_.auditdata | ConvertFrom-Json
  $TargetMailbox=$AuditData.MailboxOwnerUPN

  #Filter to view deleted emails from specific mailbox
  if(($mailbox.Length -ne 0) -and ($Mailbox -ne $TargetMailbox))
  {
   return
  }
  
  $EmailSubject=$AuditData.AffectedItems.Subject
  if($EmailSubject -eq $null)
  {
   $EmailSubject="-"
  }
  $ConversationCount=$EmailSubject.count
  $Subjects=$EmailSubject -join ", "

  #Filter emails by subject
  if(($Subject.Length -ne 0) -and ($Subjects -notmatch $Subject))
  {
   return
  } 

  $ActivityTime=Get-Date($AuditData.CreationTime)  #(Get-Date($AuditData.CreationTime)).ToLocalTime() Uncomment to view the Activity Time in local time
  $PerformedBy=$AuditData.userId
  $ResultStatus=$AuditData.ResultStatus
  $Folder=$AuditData.Folder.Path.Split("\")[1]
  $EventData=$AuditData.EventData
  
  #Export result to csv
  $OutputEvents++
  $ExportResult=@{'Activity Time'=$ActivityTime;'Target Mailbox'=$TargetMailbox;'Activity'=$Operation;'Performed By'=$PerformedBy;'No. of Emails Deleted'=$ConversationCount;'Email Subjects'=$Subjects;'Folder'=$Folder;'Result Status'=$ResultStatus;'Workload'=$Workload;'More Info'=$MoreInfo}
  $ExportResults= New-Object PSObject -Property $ExportResult  
  $ExportResults | Select-Object 'Activity Time','Activity','Target Mailbox','Performed By','No. of Emails Deleted','Email Subjects','Folder','Result Status','More Info' | Export-Csv -Path $OutputCSV -Notype -Append 
 }
 $currentResultCount=$CurrentResultCount+$ResultCount
 if($CurrentResultCount -ge 50000)
 {
  Write-Host Retrieved max record for current range.Proceeding further may cause data loss or rerun the script with reduced time interval. -ForegroundColor Red
  $Confirm=Read-Host `nAre you sure you want to continue? [Y] Yes [N] No
  if($Confirm -match "[Y]")
  {
   Write-Host Proceeding audit log collection with data loss
   [DateTime]$CurrentStart=$CurrentEnd
   [DateTime]$CurrentEnd=$CurrentStart.AddMinutes($IntervalTimeInMinutes)
   $CurrentResultCount=0
   if($CurrentEnd -gt $EndDate)
   {
    $CurrentEnd=$EndDate
   }
  }
  else
  {
   Write-Host Please rerun the script with reduced time interval -ForegroundColor Red
   Exit
  }
 }

 
 if($ResultCount -lt 5000)
 {
  if($CurrentEnd -eq $EndDate)
  {
   break
  }
  $CurrentStart=$CurrentEnd 
  if($CurrentStart -gt (Get-Date))
  {
   break
  }
  $CurrentEnd=$CurrentStart.AddMinutes($IntervalTimeInMinutes)
  $CurrentResultCount=0
  if($CurrentEnd -gt $EndDate)
  {
   $CurrentEnd=$EndDate
  }
 }
}

#Open output file after execution
If($OutputEvents -eq 0)
{
 Write-Host No records found
}
else
{
 Write-Host `nThe output file contains $OutputEvents audit records
 if((Test-Path -Path $OutputCSV) -eq "True") 
 {
  Write-Host `n" The Output file available in:"  -NoNewline -ForegroundColor Yellow; Write-Host $OutputCSV 
  Write-Host `n~~ Script prepared by AdminDroid Community ~~`n -ForegroundColor Green  
  Write-Host "~~ Check out " -NoNewline -ForegroundColor Green; Write-Host "admindroid.com" -ForegroundColor Yellow -NoNewline; 
  Write-Host " to get access to 1800+ Microsoft 365 reports. ~~" -ForegroundColor Green `n`n
  $Prompt = New-Object -ComObject wscript.shell   
  $UserInput = $Prompt.popup("Do you want to open output file?",`   
 0,"Open Output File",4)   
  If ($UserInput -eq 6)   
  {   
   Invoke-Item "$OutputCSV"   
  } 
 }
}

#Disconnect Exchange Online session
Disconnect-ExchangeOnline -Confirm:$false -InformationAction Ignore -ErrorAction SilentlyContinue