Testing emails is not an expense. It pays. Your email list and your brand have real value, and every time you screw up, you are spending real money.
Use a spreadsheet and make sure you’ve tested your software and your methods out well before you send – test on 4-5 major email clients, text and HTML. Despite what the marketing for email software and services tells you, it’s not a fire-and-forget operation. You must take the time to do email marketing right.