First keep in mind that when you batch print invoices, whether an invoices gets printed or emailed is determined by each customer's "Batch delivery method" setting on the Sales Info tab of the Maintain Customers screen. So make sure that is set appropriately.

Having said that, you will probably not want to email these invoices directly because you would end up with 50 individual emails, each with one invoice attached. Instead I would recommend you print all the invoices to one PDF, then manually send that as an email attachment.

Windows 10 will have "Microsoft Print to PDF" set up as a printer which you can choose when printing invoices (or anything else). If you're using Windows 7 you can download a free PDF printer app. I like PDF reDirect because it doesn't try to install any other unwanted programs.

Start the batch printing process just like you did before. In the Preview and Print Invoices and Packing Slips window, set Invoices to print/e-mail to "Printed Invoices". Then select a range of invoice numbers that will include the invoices you want to send. Then at Filter Customers By enter this customer's ID in both the From and To boxes. Click the Refresh button and make sure all of the invoices you want are displayed, and uncheck any that you don't want to include. Now go the Printer Setup tab and change your printer to "Microsoft Print to PDF" or whatever PDF printer you are using. Click the Print/E-mail button. A window will open asking you where you want to save the file. Pick a location and give it a file name. The whole print job will be sent to that file. Then you can email one file instead of 50.

Thanks very much StephenC!! This was the solution I was looking for :)