Not only for Windows but for Linux too. We have huge problems with forwarded mails without any Spam-Filter check which allow a lot of Spam to be forwarded.

Done:

1. Implement functionality of filtering forwarded emails when "Apply individual settings to spam filtering" option is enabled:

https://plesk.uservoice.com/forums/184549-feature-suggestions/suggestions/20397697-implement-functionality-of-filtering-forwarded-ema

2. Implement option to enable and disable "auto delete any emails flagged as spam by SA" when "Apply individual settings to spam filtering" option is disabled:

https://plesk.uservoice.com/forums/184549-feature-suggestions/suggestions/20397703-implement-option-to-enable-and-disable-auto-delet

1. There are two modes of SpamAssassin email checks:

- Global mode. "Switch on server-wide SpamAssassin spam filtering" setting is enabled: SA checks mail server queue before it appears in the mailbox.

- Mailbox-level mode. "Apply individual settings to spam filtering" setting is addtionally enabled: SA checks mail after it arrived in the mailbox.

In first case, mail will be forwarded after SA checks, in the second case - before SA checks.

When the option "filtering at the individual mailbox level" is enabled filtering of forwarded emails is not performed.

2. There is a workaround for this issue:
"Turn off the ability for individual mailboxes to manage their own spam settings and only rely on the overall global setting. On the global setting – turn on the spam filtering"

Under this scenario – both the mailbox AND the forwarders will go through the filtering.

However, there is downside/disadvantage of this workaround:
the global settings may not be "enough" for specific mailboxes and there are plenty of occasions where an individual setting of an individual mailbox is required.

In addition, there is another issue with SA "Global mode" setup in Plesk.

On a mailbox level you can enable an option to auto delete any emails flagged as spam by spam assassin, whereas you cannot do that on a global level.

This effectively means that we’ve gone from not filtering at all, to now running the emails through the filter BUT not doing anything about it…"

3. Currently, there is no way to handle the following scenario:

SPAM delivered to mail account mail1, forwarded to other mailboxes, after that it is considered as SPAM and deleted for mail1.
Recepients receive SPAM from mail1 and add it or server's IP to blacklist and client cannot send a mail to certain mailboxes.

Summary:
- Please implement functionality of filtering forwarded emails when "Apply individual settings to spam filtering" option is enabled;
- Please implement option to enable and disable "auto delete any emails flagged as spam by SA" when "Apply individual settings to spam filtering" option is disabled;
- Please implement functionality to handle the following scenario:
***
SPAM delivered to mail account mail1, forwarded to other mailboxes, after that it is considered as SPAM and deleted for mail1.
Recepients receive SPAM from mail1 and add it or server's IP to blacklist and client cannot send a mail to certain mailboxes.
***

There are two modes how SpamAssassin performs checks of the mail:
If global (server wide) spam settings are use, SA checks mail server queue, before it appears in the mailbox.
If local (individual) spam settings are used, SA checks mail after it arrived in the mailbox.

In first case mail will be forwarded after SA checks, in second case - before SA checks.

Currently, there is no way to handle this scenario:
SPAM delivered to mail account mail1, forwarded to other mailboxes, after that it is considered as SPAM and deleted for mail1.
Recepients receives SPAM from mail1 and add it or server's IP to blacklist and client cannot send a mail to certain mailboxes.