As stated here https://www.emailonacid.com/blog/article/email-development/line-length-in-html-email, setting max line length to 78 char prevents some email clients in some cases to truncate, or disastrously wrap lines which may cause problems in html rendering.
.pipe($.injectString.replace, '<!-- <style> -->', '<style>'+mqCss+'</style>')
.pipe($.htmlmin, {
collapseWhitespace: false,
- minifyCSS: false
+ minifyCSS: false,
+ maxLineLength: 78
});
return pipe();