Good morning, @gary5077. 

Thanks for coming to the Community with your question about sending emails through your QuickBooks Desktop account. 

QuickBooks requires recipients to be separated by a comma and a space, rather then a semicolon. This may be way you were able to send the email until after deleting the semicolon plus the other name. 

I recommend trying this method to see if it works for you. 

I hope this helps. Feel free to come back if you have any other questions or concerns. Have a splendid day!