Yes, on Windows, but exact step depends if MS Office is installed or not.
If you have MS Office installed, then The .eml format is actually a plain text version of .mhtml. So if you change the extension to .mht then MS Office will handle the conversion.
Otherwise, on Windows OS you can install our virtual printer driver. You will also need a 3rd party application that can print EML files.
This forum post explains in more detail.
If it isn't clear in the post above, to install the virtual printer (only needed to be done once on a machine, where the process has elevated rights), see our Convert test.
// optional set your own custom printer name
//pdftron.PDF.Convert.Printer.SetPrinterName("My Custom Printer Name");
if (!pdftron.PDF.Convert.Printer.IsInstalled()) pdftron.PDF.Convert.Printer.Install();