@media screen and (min-width: 750px){

  .newsletter{
    --gutter-width: 8rem;
  }

.newsletter__block--left{
  max-width: calc(38rem + (var(--gutter-width) ));
  flex-basis: calc(38rem + (var(--gutter-width)));
}

.newsletter__block--right{
  max-width: calc(100% - 38rem - (var(--gutter-width)));
  flex-basis: calc(100% - 38rem - (var(--gutter-width)));
  border-left: solid .1rem rgb(var(--color-accent));
}

}