I gave up! No mail getting through, everything you send to the server bounces back... And there doesn't appear to be a way to roll back to the previous version; it won't let you.
<*****@*****.***>: host mail.*****.***[1***.***.***.***] said: 554 Sending
address not accepted due to spam filter (in reply to MAIL FROM command)
And that was sent to a Proton-established address.
No matter what I do, I cannot keep the stupid SpamFoo service running, and that, in turn, is killing LDAP and XMPP.
I have rolled the server back to last night's backup after backing up mail folders.
I won't be going anywhere near another upgrade until they make SpamPoo optional and disableable, don't need to be wasting a whole day messing with BETA crud I didn't want. That'll teach me for thinking that being a BETA it would be something you have to authorise before you get stuck with it.
Cracking job SmrterTools, that has blown 12 years of confidence in your work!