Hi
Afetr having spent already too much time trying to find a solution at that problem and support being not much more efficient than me to find a solution, you’re my last hope to fix that damn problem.
New server setup with latest Virtualmin/Webmin (Ubuntu server 18.04.4 LTS) configuration that is able to send outgoing emails without problems but have a weird SASL issue on incoming emails:
May 16 14:39:51 pro-3 postfix/smtpd[15432]: connect from unknown[2408:8248:3c81:711a:c8b8:c0d6:e315:25a5]
May 16 14:39:51 pro-3 postfix/smtpd[15432]: warning: xsasl_cyrus_server_get_mechanism_list: no applicable SASL mechanisms
May 16 14:39:51 pro-3 postfix/smtpd[15432]: fatal: no SASL authentication mechanisms
May 16 14:39:52 pro-3 postfix/master[5607]: warning: process /usr/lib/postfix/sbin/smtpd pid 15432 exit status 1
May 16 14:39:52 pro-3 postfix/master[5607]: warning: /usr/lib/postfix/sbin/smtpd: bad command startup -- throttling
I have tried to install all existing SASL Libs avalaible in Ubuntu but not much mose success, all explanations I found on Internet or here are either too old or not working for me 
Any ideas ??
Thanks a lot
Vincèn