[Plugin: MailPress] Headers already sent error

This error is usually found when a re-direct or session cookie change is being done after ANY html has been output to the page.

for example

<p>Hi everyone</p>
<?php
header('Location: url');
?>

Will create that same header problem.

I hope that helps you find the problem.

output started at /wp-content/plugins/all-in-one-seo-pack/aioseop.class.php:243

apparently you are using the dev version

MP_Widget.class.php on line 263

is

setcookie(…)

Using the one that is available in the downloads section 5.2.1.

It only gives this error when the person is not logged in and is trying to subscribe. If you’re logged in there is no error or conflict with all in one seo.

Must be the lines which start here.

$user = wp_get_current_user();
		if ( !$user->ID )
		{
			$comment_cookie_lifetime = apply_filters('comment_cookie_lifetime', 30000000);
			setcookie('comment_author_'       . COOKIEHASH, $name,  time() + $comment_cookie_lifetime, COOKIEPATH, COOKIE_DOMAIN);

Found out this error occurs when jquery, css and javascript is not on. You still may want to look into this because like me others may not use neither of these options on a particular page.

solved