[RCU] [SMTP, SSL] Roundcube 1.2.2 - never use TLSv1.2 and always fallback to TLSv1 when sends mail

Paweł Łukasik pawel at lookasik.eu
Thu Nov 10 11:02:56 CET 2016


Roundcube always use TLSv1 for sending mail (used on same host as 
mailserver with both RSA and ECDSA certs, ports 25 and 587). When I 
disable all TLS/SSL versions except TLSv1.2 in Postfix config, I cannot 
send mails from Roundcube (SMTP Error: Authentication failure: STARTTLS 
failed (Code: ) in /var/www/roundcube/program/lib/Roundcube/rcube.php on 
line 1649 (POST 
) but can from desktop/mobile client.
Connection from Roundcube to IMAP server is always use TLSv1.2, external 
servers (i.e. GMail) connect with TLSv1.2.

What could cause this behaviour? Is it possible to force TLSv1.2 for 

Regards, Paul

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