For the address fields, you may want to modify one of the predefined envelope sizes, but this only takes a couple of minutes. If you want to print text on the other side, you just have to set the margins in the editor. You can copy an address to the clipboard, switch to Easy Mail and copy it to a letter, envelope or label. However, it's as easy to copy it into an address list. And once you do so, the address is available with a click.
Most programs can write addresses to a text file.
If your programs can, you will find it easy to load them into Easy Mail. If you want to spend a bit of time editing your addresses for format, Easy Mail can load them for you automatically. It's a real pain in the program I'm using. For example, one layout might include your logo, another might not. You can set up a return address with your formal name, such as Joseph P. Peters and another as Joe Peters.