Mail merge cannot email

When sending a mail merge by email I get:

<class 'smtplib.SMTPServerDisconnected'>: Connection unexpectedly closed, traceback follows
  C:\Program Files (x86)\LibreOffice 5\program\python-core-3.3.3\lib\smtplib.py:375 in function getreply() [raise SMTPServerDisconnected("Connection unexpectedly closed")]
  C:\Program Files (x86)\LibreOffice 5\program\python-core-3.3.3\lib\smtplib.py:402 in function docmd() [return self.getreply()]
  C:\Program Files (x86)\LibreOffice 5\program\python-core-3.3.3\lib\smtplib.py:478 in function rset() [return self.docmd("rset")]
  C:\Program Files (x86)\LibreOffice 5\program\python-core-3.3.3\lib\smtplib.py:762 in function sendmail() [self.rset()]
  C:\Program Files (x86)\LibreOffice 5\program\mailmerge.py:284 in function sendMailMessage() [self.server.sendmail(sendermail, truerecipients, msg.as_string())]

I had expected the emails to be sent.

Version: 5.0.3.2
Build ID: e5f16313668ac592c1bfb310f4390624e3dbfb75
Lokalisering: da-DK (da_DK)