RENEGOTIATING when providing the RCPT TO

RENEGOTIATING when providing the RCPT TO

I am having a problem sending an email, where thunderbird finally fails  with an error of «Sending of message failed. The message could not be sent because the connection to SMTP server was lost in the middle of the transaction. Try again or contact your network administrator.».
Tired of that one, I went to debug if the error had more details by performing a command line connection:

> openssl s_client -connect -crlf
(SSL information skipped from the forum)
220 SMTP Server ready November 25, 2012 2:10:52 PM PST
EHLO somehost Hello somehost ( (
250-SIZE 25000000
235 Authentication Successful
250 Sender <> OK
140120949290664:error:1409E0E5:SSL routines:SSL3_WRITE_BYTES:ssl handshake failure:s3_pkt.c:592:

(I redacted the host, ip and email address when posting)
Note that “RENEGOTIATING” is a message sent through stderr, generated by openssl, not the server.
It happens always after sending the RCPT TO:, regardless of the email provided (tried with different
domains, including
There is a delay between “RENEGOTIATING” and the “SSL3_WRITE_BYTES” error, likely a timeout. I guess
that's the server is dropping the connection.

Oddly enough, thunderbird is able to send most messages (apparently all but that one I was trying to
investigate). But Zoho is consistently rejecting me on the command line. What is going on?


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