Damn, it's even worse than that. Since the update, mails relayed by our incoming filtering gateways and tagged as SPAM aren't considered as SPAM by SmarterMail anymore with this message in the log:
[2020.09.18] 06:13:58.262  Spam Checks skipped: IP Spam Bypassed
and this in the mail headers
X-SmarterMail-TotalSpamWeight: 0 (IP Spam Bypassed)
At no time we configured our gateway IP addresses to be skipped for SPAM checks. We use custom spam checks on SmarterMail to classify the mails based on headers added by our incoming gateway.
Now every SPAM is getting through.
We have SMTP bypass (to disable IDS for our mail filters, but SMTP Spam Bypass is _NOT_ enabled. Why after the update it suddently skips spam checks ?
Fixed: Spam checks are running against incoming gateway rather than the sender's IP when gateway is added to IP bypass list.
I don't understand this change, what does mean "running spam checks against incoming gateway"?
1) we have front end filters that add headers to the mail to classify then
2) we disable all built-in spam checks in SmarterMail and add custom spam checks based on the content of these headers
3) we add our frontend filters IP address to the SMTP Bypass list to avoid the gateways to trigger IDS
4) we DO NOT enable Spam check bypass for the gateway IP (or it would disable the custom checks)
It worked perfectly like this. The new build broke this as it now skip checks for a mysterious reason...
We have to rollback before the inboxes starts to be filled with crappy mails and we're good for a "we received a lot of spam" support day.
Sorry for the rant, but honestly most of the time we update to have annoying bugs fixed for our customers, it adds an even worse unrelated issue.