Dear Maintainer,

I noticed posting a mail from Wanderlust was prevented by
missing mail-mailer-swallows-blank-line after updated to Trixie.

wl-draft.el uses this variable:
            ;; Insert an extra newline if we need it to work around
            ;; Sun's bug that swallows newlines.
            (if (eval mail-mailer-swallows-blank-line)
                (newline))

but mail-mailer-swallows-blank-line is obsoleted since Emacs 24.1
(https://doc.endlessparentheses.com/Var/mail-mailer-swallows-blank-line.html)
and Emacs 30 seems drop it.

I think above code lines can be removed.

For workaround I set (setq mail-mailer-swallows-blank-line nil) on
my .emacs.