well, you have to edit XOOPS_ROOT_PATH/include/site-closed.php
Line 42 aprox.
le="color: #000000"><?php $xoopsTpl->assign( array( 'xoops_theme' => $xoopsConfig['theme_set'], 'xoops_imageurl' => XOOPS_THEME_URL.'/'.$xoopsConfig['theme_set'].'/', 'xoops_themecss'=> xoops_getcss($xoopsConfig['theme_set']), 'xoops_requesturi' => htmlspecialchars( $_SERVER['REQUEST_URI'], ENT_QUOTES), 'xoops_sitename' => htmlspecialchars($xoopsConfig['sitename'], ENT_QUOTES), 'xoops_slogan' => htmlspecialchars($xoopsConfig['slogan'], ENT_QUOTES), 'xoops_dirname' => @$xoopsModule ? $xoopsModule->getVar( 'dirname' ) : 'system', 'xoops_banner' => $xoopsConfig['banners'] ? xoops_getbanner() : ' ', 'xoops_pagetitle' => isset($xoopsModule) && is_object($xoopsModule) ? $xoopsModule->getVar('name') : htmlspecialchars( $xoopsConfig['slogan'], ENT_QUOTES ), 'lang_login' => _LOGIN, 'lang_username' => _USERNAME, 'lang_password' => _PASSWORD, 'lang_siteclosemsg' => $xoopsConfig['closesite_text'], ) );
change by
le="color: #000000"><?php $xoopsTpl->assign( array( 'xoops_theme' => $xoopsConfig['theme_set'], 'xoops_imageurl' => XOOPS_THEME_URL.'/'.$xoopsConfig['theme_set'].'/', 'xoops_themecss'=> xoops_getcss($xoopsConfig['theme_set']), 'xoops_requesturi' => htmlspecialchars( $_SERVER['REQUEST_URI'], ENT_QUOTES), 'xoops_sitename' => htmlspecialchars($xoopsConfig['sitename'], ENT_QUOTES), 'xoops_slogan' => htmlspecialchars($xoopsConfig['slogan'], ENT_QUOTES), 'xoops_dirname' => @$xoopsModule ? $xoopsModule->getVar( 'dirname' ) : 'system', 'xoops_banner' => $xoopsConfig['banners'] ? xoops_getbanner() : ' ', 'xoops_pagetitle' => isset($xoopsModule) && is_object($xoopsModule) ? $xoopsModule->getVar('name') : htmlspecialchars( $xoopsConfig['slogan'], ENT_QUOTES ), 'lang_login' => _LOGIN, 'lang_username' => _USERNAME, 'lang_password' => _PASSWORD, 'lang_siteclosemsg' => $xoopsConfig['closesite_text'], 'xoops_adminmail' => $xoopsConfig['adminmail'], ) );
As you can see, add
'xoops_adminmail' => $xoopsConfig['adminmail'],so You can use
<{$adminmail}> in system_siteclosed.html