Postfix Mailserver Error in Thunderbird: 4.3.5 too many recipients

I got this error after a year running my server. With a search you find to adjust the
/etc/postfix/header_checks but i havent got such a entry there. So i just tried and found out, that I have configured a limit to smptd in /etc/postfix/main.cf:

Configure there the limit smtpd_recipient_limit for example to 50 (I had 16 before)

    smtpd_recipient_limit = 50

, after a restart of postifx ( sudo service postfix restart ) it worked.