I was inspecting the syslog after the OMV5 upgrade, and the only task which is giving errors is the postfix/smtpd service.
In OMV4 I got all the notifications working (plus a telegram channel to replicate them with a bot), but in OMV5 I cannot make them to work, except the "Your user account was used to log in to the openmediavault control panel via a web browser" which works like a charm.
I have the SMTP settings well configured (smtp.gmail:587, username without the domain and password) as the login email gets sent correctly. But the rest of notifications (disk resources, cpu usage, smart...) does not get sent.
I tried to reinstall and restart postfix, and clean, save, fill in and save the notifications dialog in the GUI.
These are the errors related in syslog:
postfix/smtpd[20056]: warning: dict_nis_init: NIS domain name not set - NIS lookups disabled
postfix/smtpd[20056]: fatal: in parameter smtpd_relay_restrictions or smtpd_recipient_restrictions, specify at least one working instance of: reject_unauth_destination, defer_unauth_destination, reject, defer, defer_if_permit or check_relay_domains
postfix/master[7274]: warning: process /usr/lib/postfix/sbin/smtpd pid 20056 exit status 1
postfix/master[7274]: warning: /usr/lib/postfix/sbin/smtpd: bad command startup -- throttling
monit[1557]: Cannot create socket to [127.0.0.1]:25 -- Connection timed out
monit[1557]: Cannot open a connection to the mailserver 127.0.0.1:25 -- Operation now in progress
monit[1557]: Mail: Delivery failed -- no mail server is available
monit[1557]: Alert handler failed, retry scheduled for next cycle
Thanks in advance.