Zoho Spam Email Headers x-zohomail etc

I have recently migrated a small domain over to Zoho and have been really disappointed with the very poor spam handling. I have had to resort to whitelisting most domains (so far several dozen) that send email to us despite being in .au domains with well regulated spam policies by the ACMA in Australia and despite SPF pass for these domains and despite there not being anything about the emails that I would expect should trigger bayesian filters.
I sent an email about this and several other questions to the zoho support email a few weeks ago and am yet to receive any reply.

There seems to be very little control in the spam settings within the cpanel of zoho other than whitelisting. Also there does not even seem to be any ability for wildcards or allowing subdomains in the whitelists.

As an IT admin for several decades, it is sadly the worst spam system I have ever seen. It has the following terrible combination of broad faults:

Extremely poor accuracy
Very inflexible configuration (whitelists only)
Very poor and scant documentation
Non-understandable information placed into email headers
Spam/Not Spam can only be reported in the web interface (which is quite slow) and there appears no facility for users to do so using IMAP

Can anyone give me more detailed information on this zoho spam system such as:

A full description of the acronymns in the zoho spam headers so I can understand them: eg:
x-zohomail: SS_1 SFPD SFPSF ZSPF-002 LBC UW SF_SIP_EXT SGR1_1_11025_646
x-zohomail: SS_1 SFPD SFPGN UW24 UB2468 ZMHF-MSGIDDMNPTN_1 COSF ZCF-710LNDF ODL SGR3_1_11025_617
How the zoho system makes its determination of spam/ham
Whether marking items as spam/not spam actually does anything (it appears to do nothing)
What bayesian filtering is done?
Whether there are any ways to have additional headers inserted, eg: something like the headers of conventional spam systems like spamassassin would be helpful.

Thanks

Jesse

Also