qTranslate and MailPress (e-mail subscription)

I think that the better way is to sort users in different mailing list when they click subscribe. For example if English man click subscribe than place him in English mailing list. And so on this each other.
Then create one mail for each language and send them to appropriate mailing list.

The only thing I don’t know how to do is to
change default subscription based on, say, browser language.

What do you mean under “default subscription”?

You can add user to a different mailing list by showing different subscription forms.
Just add this shortcode [mailpress mailinglist=id] to the page template (use do_shortcode() ).
Change ‘id’ on the fly, based on page language.

qTranslate + MailPress support has been addressed many many times.
Here are some hints, requires good coding skills, and tests, tests, tests … and sometimes ability to analyse qTranlsate and MailPress code .
Good luck ! …

Language selection in qTranslate :
* language selection is based on ( ?lang=xxx , $_GET[‘lang’] ) so language is in the url and so is browser oriented …

Integration into MailPress : not that simple !

* Mails having templates such as ‘confirmed’, ‘moderate’, ‘new_user’, ‘retrieve_pwd’ … requires to test the $_GET[‘lang’] value to set the appropriate translations in the current mailpress theme templates.

* Mail template ‘comments’ cannot be sent in the subscriber language …

* Mails > add new : cannot be sent in the subscriber language …

* for newsletters :
++ for each language supported
— for each periodicity (new_post, daily, weekly, monthly)
==== create a newsletter (mp-content/advanced/newsletters/) to allow subscribers to subscribe to the newsletters in their language. Each newsletter will address its corresponding mailpress theme and or template :

<mail>
		<Theme>mytheme_en</Theme>
		<Template>weekly</Template>
		<subject><![CDATA[<?php printf( __('[%1$s] Weekly newsletter in english', MP_TXTDOM), get_bloginfo('name')); ?>]]></subject>
	</mail>

or template within the mailpress current theme :

<mail>
		<Template>weekly_en</Template>
		<subject><![CDATA[<?php printf( __('[%1$s] Weekly newsletter in english', MP_TXTDOM), get_bloginfo('name')); ?>]]></subject>
	</mail>

+ their own threshold

<processor>
		...
		<threshold>MailPress_weekly_en</threshold><!-- stored on wordpress options table -->
		...

— create a mailpress theme and/or corresponding newsletter templates (mp-content/themes/)
==== force the value of $_GET[‘lang’] : several ways to do so among which :
$$$$$ in the _loop.php file of the dedicated theme
$$$$$ in the template file
$$$$$ or use the parent/child theme api http://goo.gl/0j6o2 to do so …
==== have a specific test in the loop if title/post do not exist in the specified language and a counter tallying if there is at least a post in the newsletter. something like that :

<?php
$_GET['lang'] = 'en'; // force the value of $_GET['lang']
$count_post = 0;
while (have_posts()) :
   the_post();
// <!-- maybe some html comments to clean up in
//      get_the_content() before test -->
   if (empty(get_the_content())) continue;
   $count_post++;
?>
.....
<?php
endwhile;
if (!$count_post) {
   ob_end_clean();
   return '';
}
?>

==== there might have some issues using {{the_title}}