https://bugs.gentoo.org/782643
--- a/configure.ac
+++ b/configure.ac
@@ -1270,20 +1270,9 @@ if test "x$enable_smtp" != "xno" && test "x$with_libesmtp" != "xno"; then
 		CPPFLAGS="$CPPFLAGS_SAVE"
 		LDFLAGS="$LDFLAGS_SAVE"
 	else
-		AC_MSG_CHECKING(for libESMTP)
-		if libesmtp-config --version >/dev/null 2>&1; then
-			AC_MSG_RESULT(yes)
-			LIBESMTP_CFLAGS="`libesmtp-config --cflags`"
-			LIBESMTP_LIBS="`libesmtp-config --libs`"
-		else
-			AC_MSG_RESULT(no)
-			libesmtp=no
-		fi
-	fi
-	if test "x$enable_smtp" = "xyes" && test "x$libesmtp" = "xno"; then
-		AC_MSG_ERROR(libESMTP not found)
+		PKG_CHECK_MODULES(libesmtp, libesmtp-1.0)
 	fi
-	enable_smtp=$libesmtp
+	enable_smtp="yes"
 fi
 
 dnl ***************************************************************************