Here is how to change the button border thickness in an email campaign in mailchimp
- First click on "Home" in the left sidebar menu
- Then click on the "Edit" button for the campaign
- Then click on the "Edit design" button at the bottom of the screen
- Then click on "Styles" in the left sidebar menu
- Then click on the "Button" option in the left sidebar menu
- Finally click on the up or down arrow to change the value
