Message archive are eml files.
So you can purge with a powershell script :
# Change the value $oldTime in order to set a limit for files to be deleted.
$oldTime = [int]60 # 60 days
foreach ($path in Get-Content "C:\pathList.txt") {
# Write information of what it is about to do
Write-Host "Trying to delete files older than $oldTime days, in the folder $path" -ForegroundColor Green
# deleting the old files
Get-ChildItem $path -Recurse -Include "*.*" | WHERE {($_.CreationTime -le $(Get-Date).AddDays(-$oldTime))} | Remove-Item -Force -recurse