This PowerShell script synchronizes the Out-Of-Office status of your Zendesk agent Exchange mailboxes with the Zendesk Out-Of-Office Extension. This provides a much better user experience to your agents than requiring them to set their statuses separately in Outlook and Zendesk. Run this as a scheduled task.

ZendeskAPI-SyncOutOfOffice.ps1

#Download all admin and agent user objects from Zendesk.
$agents = &ZendeskAPI-GetZendeskUsers.ps1 "allagents"

#Trim agent list.
$agents = $agents | where email -like "*@yourdomain.com" | sort email

#Connect to Exchange Online. Use your own script here or swap this line out with the connection commands supplied by Microsoft.
#There's no reason this won't work with Exchange On-Prem AFAIK. We just use Exchange Online, so the comments reference it.
&ConnectToExchangeOnline.ps1

#New array to hold agent email, last Out of Office status, current Out of Office status.
$oooStatuses = @()

$i = 0
$agents | ForEach-Object {
    #Get last OoO status from Zendesk agent user fields.
    $lastOoOStatus = $_.user_fields.agent_ooo
    #Get current OoO status from Exchange Online.
    $currentOoOStatus = $_.email | Get-MailboxAutoReplyConfiguration | select AutoReplyState, StartTime, EndTime
    #Create a custom object to hold all of that.
    $oooStatus = [PSCustomObject]@{
        email = $_.email
        lastOoOStatus = $lastOoOStatus.ToString()
        currentOoOStatus = $currentOoOStatus.AutoReplyState
        startTime = $currentOoOStatus.StartTime
        endTime = $currentOoOStatus.EndTime
        }
    #Add the custom object to the array.
    $oooStatuses += $oooStatus
    #Show a progress bar.
    Write-Progress -Activity "Getting Out of Office status from Exchange Online..." -PercentComplete (($i/$agents.Count)*100) -Status $_.email
    $i++
    }
#Close the progress bar.
Write-Progress -Activity "Getting Out of Office status from Exchange Online..." -Completed

#Zendesk API Connection Headers Referencing System Environmental Variables for username and API token.
$headers = @{Authorization = 'Basic ' + [Convert]::ToBase64String([Text.Encoding]::ASCII.GetBytes("$($env:ZendeskAPI_Username):$($env:ZendeskAPI_Token)"));}

#Zendesk API: create_or_update
$seturi = "https://yourdomain.zendesk.com/api/v2/users/create_or_update.json"

#Look for changes in Out of Office status, do stuff if changes are found.
$oooStatuses | ForEach-Object {
    #Convert Exchange Online OoO status into a true or false.
    if($_.currentOoOStatus -eq "Enabled"){
        $isooo = "true"
        }
    elseif(($_.currentOoOStatus -eq "Scheduled") -and ($_.startTime -lt (Get-Date) -and $_.endTime -gt (Get-Date))){
        $isooo = "true"
    }
    else {
        $isooo = "false"    
    }

    #Compare last OoO satus and current OoO status.
    if(($_.lastOoOStatus -ne $isooo) -and ($isooo -eq "true")){
        Write-Host $_.email "enabled their Out of Office auto-reply." -ForegroundColor Cyan
    }
    if(($_.lastOoOStatus -ne $isooo) -and ($isooo -eq "false")){
        Write-Host $_.email "disabled their Out of Office auto-reply." -ForegroundColor Magenta
    }
    
    #If a change in OoO status is detected, update Zendesk.
    if($_.lastOoOStatus -ne $isooo){
        #Build the JSON.
        $setjson = '{"user": {
            "email": "'+$_.email+'",
            "user_fields": {
                "agent_ooo": "'+$isooo+'"
                }
            }
        }'

        #Echo the current custom object and the JSON.
        $_
        $setjson

        #Post the JSON body to the Zendesk API
        Invoke-RestMethod -Uri $seturi -Method Post -Headers $headers -ContentType "application/json" -Body $setjson
    }
}

Here's the Zendesk agent query script referenced in line 2.