Postfix SMTP Auth Error “no SASL authentication mechanisms”

I have been setting up a new mail server recently with Postfix and SMTP Auth, and got the error message "no SASL authentication mechanisms".

If you have enabled SMTP Auth with Postfix like this:

smtpd_sasl_auth_enable = yes
smtpd_sasl_security_options = noanonymous
smtpd_sasl_local_domain = $myhostname
broken_sasl_auth_clients = yes
smtpd_recipient_restrictions =
    permit_sasl_authenticated,
    permit_mynetworks,
    reject_unauth_destination

and are getting messages like this (the extract below is from the mail log file):

Nov  2 15:31:09 vps131 postfix/smtpd[14007]: warning: dict_nis_init: NIS domain name not set - NIS lookups disabled
Nov  2 15:31:09 vps131 postfix/smtpd[14007]: warning: xsasl_cyrus_server_get_mechanism_list: no applicable SASL mechanisms
Nov  2 15:31:09 vps131 postfix/smtpd[14007]: fatal: no SASL authentication mechanisms
Nov  2 15:31:10 vps131 postfix/master[12004]: warning: process /usr/libexec/postfix/smtpd pid 14007 exit status 1
Nov  2 15:31:10 vps131 postfix/master[12004]: warning: /usr/libexec/postfix/smtpd: bad command startup -- throttling

then you need to install the cyrus-sasl-plain package like so:

yum install cyrus-sasl-plain

The above method will install the cyrus-sasl-plain packages on CentOS and other RPM/Yum based Linux distributions, so you would need to use the appropriate package manager (and software package) for other Linux distros.