I have two columns in this snippet below of my email template. Left - text of variable length. Right - fixed button.

I need the columns to responsively wrap on mobile, so they should be seperate. So right column doesn't know height of left. How can I get it center vertically to match no matter height of left column?

valign="middle" has not worked unless I set a fixed height.

https://litmus.com/community/snippets/218-how-to-vertically-center-this-button

Thanks for any help