I have just found this old thread. I have a similar problem in that I cannot send Calibre email to my Kindle. The Calibre message I get is:
Spoiler:
Traceback (most recent call last):
File "site-packages/calibre/gui2/wizard/send_email.py", line 207, in test_email_settings
File "site-packages/calibre/utils/smtp.py", line 157, in sendmail
File "site-packages/calibre/utils/smtplib.py", line 761, in sendmail
SMTPSenderRefused: (501, 'Syntax error in parameters or arguments', u'calibre')
Log:
connect: (u'smtp.1and1.com', 587)
connect: (u'smtp.1and1.com', 587)
reply: '220 perfora.net (mreueus003) Nemesis ESMTP Service ready\r\n'
reply: retcode (220); Msg: perfora.net (mreueus003) Nemesis ESMTP Service ready
connect: perfora.net (mreueus003) Nemesis ESMTP Service ready
send: 'ehlo clarks-macbook.local\r\n'
reply: '250-perfora.net Hello clarks-macbook.local [73.155.252.72]\r\n'
reply: '250-AUTH LOGIN PLAIN\r\n'
reply: '250-SIZE 69920427\r\n'
reply: '250 STARTTLS\r\n'
reply: retcode (250); Msg: perfora.net Hello clarks-macbook.local [73.155.252.72]
AUTH LOGIN PLAIN
SIZE 69920427
STARTTLS
send: 'STARTTLS\r\n'
reply: '220 OK\r\n'
reply: retcode (220); Msg: OK
send: 'ehlo clarks-macbook.local\r\n'
reply: '250-perfora.net Hello clarks-macbook.local [73.155.252.72]\r\n'
reply: '250-AUTH LOGIN PLAIN\r\n'
reply: '250 SIZE 69920427\r\n'
reply: retcode (250); Msg: perfora.net Hello clarks-macbook.local [73.155.252.72]
AUTH LOGIN PLAIN
SIZE 69920427
send: 'AUTH PLAIN AGNid2ViY29tbWVyY2VAbWFpcGVucmFpLmNvbQA5OWIwYjB0dw ==\r\n'
reply: '235 Authentication succeeded\r\n'
reply: retcode (235); Msg: Authentication succeeded
send: u'mail FROM:<calibre> size=537\r\n'
reply: '501 Syntax error in parameters or arguments\r\n'
reply: retcode (501); Msg: Syntax error in parameters or arguments
send: 'rset\r\n'
reply: '250 OK\r\n'
reply: retcode (250); Msg: OK
send: 'quit\r\n'
reply: '221 perfora.net Service closing transmission channel\r\n'
reply: retcode (221); Msg: perfora.net Service closing transmission channel
I'd appreciate any advice. Thanks.