Bad parameters to mail()

turn on the mail logging in the sn settings. Report the email content you find in the log.

You first need to solve the oldest of the above errors, this is fundamental. The simplenews error may well be a result of this.

No response, closing the issue.

Found out solution:

You need to modify 'mail.inc' file contained in '/includes' directory of the Drupal installation.

Change the line 186 from:
mime_header_encode($message['subject']),
To:
str_replace("\n", '',mime_header_encode($message['subject'])),

I know it's hard coding in the core files but it works.
Now you can include parameters in the email title - like '!site' - and message will be send :-)
CYa!

Patches hacking the core related to functionality of some contributed module are not good solutions, especially marking them as fixed:)
http://drupal.org/patch/review

The error means that mail() function received the wrong arguments from simplenews.
You have to check what parameters has been send to mail() function (php.net/mail).
Look for the line:

    drupal_mail('simplenews', 'subscribe', $mail, $subscription->language, $params, $params['from']['address']);

And paste it before that line:

    watchdog('simplenews', "drupal_mail('simplenews', 'subscribe', $mail, $subscription->language, $params, {$params['from']['address']})");

And check your logs, what has been passed to your drupal_mail.
And compare with requirements: http://api.drupal.org/api/function/drupal_mail
I didn't test that code, so look after some syntax mistakes, just for general idea to know what you looking for.

There is already an issue report opened for Drupal. It seems the problem is mail().
See #84883: Unicode::mimeHeaderEncode() doesn't correctly follow RFC 2047 for more informations.

I am changing the category as this is not a bug of the module which simply uses a Drupal function.
The problem, if that can be fixed, must be fixed in Drupal core code.

#84883: Unicode::mimeHeaderEncode() doesn't correctly follow RFC 2047