Attache multipe attachements

Hi all,
first of all, great software, many thanks to all involved people!

I have a question reagarding multiple attachments.
In my wordpress installation I created a new plugin using
add_action("wpcf7_before_semd_mail", "wpcf7_do_something_else", 1)
and inside of that function I am using the email feature. Input is an array $files[] with multiple paths inside to my PDFs which I would like to add as attachment. I tried already several ways but either I get only the first PDF or none.

This one gives me only the first PDF as attachment:

[...]
$cf7_mailprops = $cf7->get_properties();
[...]
foreach ($files as $file){
   $cf7_mailprops['mail']['attachment'] = $file;
}

This one gives me none as attachment:

[...]
$cf7_mailprops = $cf7->get_properties();
[...]
$cf7_mailprops['mail']['attachment'] = implode(', ', $files);
}

How can I use multiple arrays of $cf7_mailprops[‘mail’][‘attachment’]
Any ideas?

Br
Jan