I built a new server using Ubuntu 18.04 (minimal install), then added minimal kbuntu desktop.
Installed Virtualmin using the script, no issues through this process.
(All saved domains come from Centos7) - Restored all domains from old server, everything seems to be created correctly.
Postfix is receiving emails all OK, and I can read them using the Servers >> Read User Mail within Webmin.
All emails are being stored in the following location : /home/tpv/homes/test/Maildir (there are two domains sharing 5 email accounts, this was a test)
If I try and access using Usermin (which I use when away from home) it's a blank screen for minutes on end, and when the interface does appear there are no email boxes shown. I don't know if Usermin goes through Dovecot, but I did try every setting there to change mail delivery location, except the last one for user defined. Made no difference.
I tried creating a new email user (test) but that too was not "seen" by Usermin. I did notice that the login name had changed from test.twin-peaks-video to firstname.lastname@example.org.
I ran the command "Mail Client Configuration, said it had completed correctly. But Thunderbird does not see the configuration file when trying to create a new user. Thunderbird is also unable to connect to email.
The only error message I'm getting is from Dovecot: (I've checked path names etc but could see no issues there ... not much help on internet for this one)
imap-login: Fatal: Couldn't parse private ssl_key: error:0909006C:PEM routines:get_name:no start line: Expecting: ANY PRIVATE KEY master: Error: service(imap-login): command startup failed, throttling for 60 secs
Any help would be gratefully received ...