Recursively add suffix after extension to all files in a directory

Run the below command in PowerShell

Get-ChildItem -File -Recurse | ForEach-Object `
   { Rename-Item $_.FullName $($_.BaseName + ".[xyz@gmail].xyz") -WhatIf }

The -WhatIf option is to do a dry run. After checking that the new names are correct, just remove -WhatIf to do the real rename. The equivalent shortened version is

ls -Fi -R | % { ren $_.FullName $($_.BaseName + ".[xyz@gmail].xyz") -wi }