Send Email Messages

I am running LibreOffice Writer
Version: (x64)
Build ID: a64200df03143b798afd1ec74a12ab50359878ed
CPU threads: 8; OS: Windows 10.0; UI render: default; VCL: win;
Locale: en-US (en_US); UI-Language: en-US
Calc: threaded

I am trying to use the Mail Merge to send Email Messages
When I test my email setting they are Successful

But when I try to send the Email Messages I get the following error message, can you please help

<class ‘smtplib.SMTPSenderRefused’>: (450, b’Requested mail action not taken: mailbox unavailable’, ‘’), traceback follows
File “C:\Program Files\LibreOffice\program\”, line 288, in sendMailMessage
self.server.sendmail(sendermail, truerecipients, msg.as_string())
File “C:\Program Files\LibreOffice\program\python-core-3.5.7\lib\”, line 863, in sendmail
raise SMTPSenderRefused(code, resp, from_addr)


Your SMTP server does not accept the message.

When I test my email setting they are Successful

How do you perform that test? If you just click the Test Settings button in Tools -> Options -> LibreOffice Writer -> Mail Merge Email then this doesn’t tell much, since that test does neither test the port, the authentication nor any check, whether SMPT server allows for the sender’s hostname (my provider for example required full qualified hostname as sender, otherwise it refuses to accept emails from my system).