Hi Danguolė,

To remove the lines would involve customising the core/email_html mustache template. 

The initial file can be found at lib/templates/email_html.mustache and can be overriden by placing a mustache template in  theme/<themename>/templates/core/email_html.mustache.

Our front-end dev recommends a partner/themer does this as it can not be done through the UI and will affect almost every e-mail that comes out of the system.

cheers,

George.