- Plesk for Linux
- Unable to send mail out from Plesk to certain domain with Qmail.
- Errors in
CONFIG_TEXT: sendmail: STARTTLS=client: 5616:error:14082174:SSL routines:SSL3_CHECK_CERT_AND_ALGORITHM:dh key too small:s3_clnt.c:2429:
CONFIG_TEXT: qmail: delivery deferral: TLS_connect_failed:_error:14082174:SSL_routines:SSL3_CHECK_CERT_AND_ALGORITHM:dh_key_too_small;_connected_to_203.0.113.2/
Different security settings on the servers: destination mail server has a Diffie-Hellman key with size less than 768 bit, but recent versions of OpenSSL in Plesk consider such keys as insecure.
Use either of the following solutions:
- Switch to Postfix
- If Qmail still needed, contact administrators of the destination mail server in order to update the keys to the more secure ones.
- Log in to Plesk server using SSH and allow it to connect to non-secure remote mail servers:
Warning: this will decrease the server security and might be used only in case of emergency!
click here to view the options
Option I: Add the remote mail server to trusted hosts list in Qmail:
# mkdir -p /var/qmail/control/notlshosts
# touch /var/qmail/control/notlshosts/mail.example.com
Note: Qmail will start sending messages without TLS encryption to such domains.
Option II: Contact system administrator to downgrade
Option III: Disable DH keys exchange for Qmail outgoing connections to destination mail servers:
# echo 'DEFAULT:!DH' > /var/qmail/control/tlsclientciphers
Note: this solution affects connections to all mail servers and potentially can lead to connection problems to some servers.
Restart Qmail to apply the changes:
# service qmail restart