Shortcodes in Browser

Hello,

thanks for the great plugin.

My problem: If i view the Newsletter in a browser the used shordcodes show just the default text. But the shortcodes seems to work because in my e-mail client i see for example the lastname correct.

Have someone an idea what is the reason for that?
Many thanks in advance!

https://ww.wp.xz.cn/plugins/wysija-newsletters/