How to avoid empty space at the end of a page when using scrlttr2?

With scrlttr2 I sometimes used \enlargethispage as a quick way to get more text onto the first page, for example:

\enlargethispage{3\baselineskip}

Done before the end of the letter or before the end of the first page, respectively, this allows three further lines on the page. There's even a starred version \enlargethispage* which tries also compression.

Alternatively, you could use the option enlargefirstpage=true which increases the text area if the footer of the first page doesn't use much space, or adjust the pseudolength firstfootvpos or use typearea package features. I quickly took the easy first way, depending on my letter's size. The other ways are described in the KOMA-Script manual.

A combination of the options enlargefirstpage and firstfoot=false is a very easy solution to enlarge the first page:

\documentclass[12pt,fromalign=right,fromrule=afteraddress,
               parskip=half,pagenumber=no,DIV=15,
               enlargefirstpage,firstfoot=false]{scrlttr2}

I've removed option foldmarks=true, because it's default. All other options are unchanged from the question.

To see the difference of using the two options as show above, compare the left and right picture:

The right one has been made with:

\documentclass[
  12pt,fromalign=right,fromrule=afteraddress,
  parskip=half,pagenumber=no,DIV=15,
  enlargefirstpage,firstfoot=false
]{scrlttr2}
\usepackage{blindtext}
\begin{document}
\begin{letter}{You\\There}
  \opening{Hey!}
  \blindtext[5]
  \closing{Bye}
\end{letter}
\end{document}

the left one without line

  enlargefirstpage,firstfoot=false

BTW: Even

  enlargefirstpage,firstfoot=yes

would result in a little bit more text on the first page:

so the comment, that firstfoot=yes would result in errors is not true. However, if you really want more text on the first page, I would recommend to use firstfoot=false as originally stated.

I created an invoice with srlttr2 and on DIN-A4 paper. Had some hours struggling around with the recommendations (enlargefirstpage, firstfoot=false), but without success.

Then I set:

  \setlength{\textheight}{24cm}
  \setlength{\footskip}{0mm}
  \setlength{\footheight}{0mm}

With textheight I can expand the text area to the bottom of the page. That was what I wanted.