Simplify form_alter logic by using hook_form_FORM_ID_alter

function webmail_plus_solr_form_alter(&$form, $form_state, $form_id) {
	
	
	if($form_id=='apachesolr_settings') {
		$form['webmail_plus_solr_notice'] = array (
		  '#type' => 'item',
		  '#value' => t('You have Webmail Plus Solr installed. To configure Solr for Webmail Plus please follow !thislink and then click on the Solr Search section.', array('!thislink' => l(t('this link'), 'admin/settings/webmail_plus'))),
		  '#weight' => -1
		);
	}
	
	if($form_id!='webmail_plus_admin_settings') return;

http://api.drupal.org/api/function/hook_form_FORM_ID_alter/6