iredmail-doc/howto/3-allow.insecure.pop3.imap.smtp.connections.md

Allow insecure POP3/IMAP/SMTP connections without STARTTLS

With default iRedMail setting, all clients are forced to use POP3/IMAP/SMTP services over STARTTLS for secure connections. If your mail clients try to access mailbox via protocol POP3/IMAP without TLS support, you will get error message like below:

Plaintext authentication disallowed on non-secure (SSL/TLS) connections

Allow insecure POP3/IMAP connections

If you want to enable POP3/IMAP services without STARTTLS for some reason (again, not recommended), please update below two parameters in Dovecot config file /etc/dovecot/dovecot.conf and restart Dovecot service:

• on Linux and OpenBSD, it's /etc/dovecot/dovecot.conf
• on FreeBSD, it's /usr/local/etc/dovecot/dovecot.conf

disable_plaintext_auth=no
ssl=yes

Again, it's strongly recommended to use only POP3S/IMAPS for better security.

Default and recommended setting configured by iRedMail is:

disable_plaintext_auth=yes
ssl=required

Allow insecure SMTP connection

Please comment out below line in Postfix config file /etc/postfix/main.cf and reload or restart Postfix service:

smtpd_tls_auth_only=yes